diff --git a/.prettierrc.json b/.prettierrc.json
index 9b614ef6..5f19d4e2 100644
--- a/.prettierrc.json
+++ b/.prettierrc.json
@@ -5,5 +5,6 @@
   "tabWidth": 2,
   "singleQuote": true,
   "jsxSingleQuote": true,
+  "endOfLine": "lf",
   "plugins": ["prettier-plugin-tailwindcss"]
 }
diff --git a/apps/readest-app/package.json b/apps/readest-app/package.json
index f27b261f..92f514d0 100644
--- a/apps/readest-app/package.json
+++ b/apps/readest-app/package.json
@@ -98,6 +98,7 @@
     "semver": "^7.7.1",
     "stripe": "^18.2.1",
     "tinycolor2": "^1.6.0",
+    "uuid": "^11.1.0",
     "zod": "^4.0.8",
     "zustand": "5.0.6"
   },
@@ -116,6 +117,7 @@
     "@types/react-window": "^1.8.8",
     "@types/semver": "^7.7.0",
     "@types/tinycolor2": "^1.4.6",
+    "@types/uuid": "^10.0.0",
     "@vitejs/plugin-react": "^4.7.0",
     "autoprefixer": "^10.4.20",
     "cpx2": "^8.0.0",
diff --git a/apps/readest-app/public/locales/ar/translation.json b/apps/readest-app/public/locales/ar/translation.json
index fcf4ea92..2693dc55 100644
--- a/apps/readest-app/public/locales/ar/translation.json
+++ b/apps/readest-app/public/locales/ar/translation.json
@@ -487,5 +487,38 @@
   "Are you sure to delete the local copy of the selected book?": "هل أنت متأكد من حذف النسخة المحلية للكتاب المحدد؟",
   "Remove from Cloud & Device": "إزالة من السحابة والجهاز",
   "Remove from Cloud Only": "إزالة من السحابة فقط",
-  "Remove from Device Only": "إزالة من الجهاز فقط"
+  "Remove from Device Only": "إزالة من الجهاز فقط",
+  "Error": "خطأ",
+  "Disconnected": "غير متصل",
+  "KOReader Sync Settings": "إعدادات مزامنة KOReader",
+  "Connected as {{username}}": "متصل كـ {{username}}",
+  "Disconnect": "قطع الاتصال",
+  "Sync Strategy": "استراتيجية المزامنة",
+  "Ask on conflict": "اسأل عند حدوث تعارض",
+  "Always use latest": "استخدام الأحدث دائمًا",
+  "Send changes only": "إرسال التغييرات فقط",
+  "Receive changes only": "استلام التغييرات فقط",
+  "Disabled": "معطل",
+  "Checksum Method": "طريقة التحقق من الصحة",
+  "File Content (recommended)": "محتوى الملف (موصى به)",
+  "File Name": "اسم الملف",
+  "Device Name": "اسم الجهاز",
+  "Sync Tolerance": "تحمل المزامنة",
+  "Precision: {{precision}} decimal places": "الدقة: {{precision}} منزلة عشرية",
+  "Connect to your KOReader Sync server.": "الاتصال بخادم مزامنة KOReader الخاص بك.",
+  "Server URL": "عنوان URL للخادم",
+  "Username": "اسم المستخدم",
+  "Your Username": "اسم المستخدم الخاص بك",
+  "Password": "كلمة المرور",
+  "Connect": "الاتصال",
+  "KOReader Sync": "مزامنة KOReader",
+  "Sync Conflict": "تعارض المزامنة",
+  "Sync reading progress from \"{{deviceName}}\"?": "مزامنة تقدم القراءة من \"{{deviceName}}\"؟",
+  "another device": "جهاز آخر",
+  "Local Progress": "التقدم المحلي",
+  "Remote Progress": "التقدم البعيد",
+  "Page {{page}} of {{total}} ({{percentage}}%)": "الصفحة {{page}} من {{total}} ({{percentage}}%)",
+  "Current position": "الموقع الحالي",
+  "Approximately page {{page}} of {{total}} ({{percentage}}%)": "تقريبًا الصفحة {{page}} من {{total}} ({{percentage}}%)",
+  "Approximately {{percentage}}%": "تقريبًا {{percentage}}%"
 }
diff --git a/apps/readest-app/public/locales/de/translation.json b/apps/readest-app/public/locales/de/translation.json
index f62c59f0..ed52767f 100644
--- a/apps/readest-app/public/locales/de/translation.json
+++ b/apps/readest-app/public/locales/de/translation.json
@@ -471,5 +471,38 @@
   "Are you sure to delete the local copy of the selected book?": "Sind Sie sicher, dass Sie die lokale Kopie des ausgewählten Buches löschen möchten?",
   "Remove from Cloud & Device": "Aus Cloud & Gerät entfernen",
   "Remove from Cloud Only": "Nur aus der Cloud entfernen",
-  "Remove from Device Only": "Nur vom Gerät entfernen"
+  "Remove from Device Only": "Nur vom Gerät entfernen",
+  "Error": "Fehler",
+  "Disconnected": "Getrennt",
+  "KOReader Sync Settings": "KOReader Sync-Einstellungen",
+  "Connected as {{username}}": "Verbunden als {{username}}",
+  "Disconnect": "Trennen",
+  "Sync Strategy": "Sync-Strategie",
+  "Ask on conflict": "Bei Konflikten fragen",
+  "Always use latest": "Immer die neueste Version verwenden",
+  "Send changes only": "Nur Änderungen senden",
+  "Receive changes only": "Nur Änderungen empfangen",
+  "Disabled": "Deaktiviert",
+  "Checksum Method": "Prüfziffernverfahren",
+  "File Content (recommended)": "Dateiinhalte (empfohlen)",
+  "File Name": "Dateiname",
+  "Device Name": "Gerätename",
+  "Sync Tolerance": "Sync-Toleranz",
+  "Precision: {{precision}} decimal places": "Präzision: {{precision}} Dezimalstellen",
+  "Connect to your KOReader Sync server.": "Mit Ihrem KOReader Sync-Server verbinden.",
+  "Server URL": "Server-URL",
+  "Username": "Benutzername",
+  "Your Username": "Ihr Benutzername",
+  "Password": "Passwort",
+  "Connect": "Verbinden",
+  "KOReader Sync": "KOReader Sync",
+  "Sync Conflict": "Sync-Konflikt",
+  "Sync reading progress from \"{{deviceName}}\"?": "Lesefortschritt von \"{{deviceName}}\" synchronisieren?",
+  "another device": "ein anderes Gerät",
+  "Local Progress": "Lokaler Fortschritt",
+  "Remote Progress": "Entfernter Fortschritt",
+  "Page {{page}} of {{total}} ({{percentage}}%)": "Seite {{page}} von {{total}} ({{percentage}}%)",
+  "Current position": "Aktuelle Position",
+  "Approximately page {{page}} of {{total}} ({{percentage}}%)": "Ungefähr Seite {{page}} von {{total}} ({{percentage}}%)",
+  "Approximately {{percentage}}%": "Ungefähr {{percentage}}%"
 }
diff --git a/apps/readest-app/public/locales/el/translation.json b/apps/readest-app/public/locales/el/translation.json
index eb5aad5f..11cb46d6 100644
--- a/apps/readest-app/public/locales/el/translation.json
+++ b/apps/readest-app/public/locales/el/translation.json
@@ -471,5 +471,38 @@
   "Are you sure to delete the local copy of the selected book?": "Είστε σίγουροι ότι θέλετε να διαγράψετε την τοπική αντιγραφή του επιλεγμένου βιβλίου;",
   "Remove from Cloud & Device": "Αφαίρεση από το Cloud & Device",
   "Remove from Cloud Only": "Αφαίρεση μόνο από το Cloud",
-  "Remove from Device Only": "Αφαίρεση μόνο από το Device"
+  "Remove from Device Only": "Αφαίρεση μόνο από το Device",
+  "Error": "Σφάλμα",
+  "Disconnected": "Αποσυνδεδεμένο",
+  "KOReader Sync Settings": "Ρυθμίσεις συγχρονισμού KOReader",
+  "Connected as {{username}}": "Συνδεδεμένος ως {{username}}",
+  "Disconnect": "Αποσύνδεση",
+  "Sync Strategy": "Στρατηγική συγχρονισμού",
+  "Ask on conflict": "Ρώτησε σε περίπτωση σύγκρουσης",
+  "Always use latest": "Χρησιμοποίησε πάντα την τελευταία έκδοση",
+  "Send changes only": "Αποστολή μόνο αλλαγών",
+  "Receive changes only": "Λήψη μόνο αλλαγών",
+  "Disabled": "Απενεργοποιημένο",
+  "Checksum Method": "Μέθοδος ελέγχου",
+  "File Content (recommended)": "Περιεχόμενο αρχείου (συνιστάται)",
+  "File Name": "Όνομα αρχείου",
+  "Device Name": "Όνομα συσκευής",
+  "Sync Tolerance": "Ανοχή συγχρονισμού",
+  "Precision: {{precision}} decimal places": "Ακρίβεια: {{precision}} δεκαδικά ψηφία",
+  "Connect to your KOReader Sync server.": "Συνδεθείτε στον διακομιστή συγχρονισμού KOReader.",
+  "Server URL": "Διεύθυνση URL διακομιστή",
+  "Username": "Όνομα χρήστη",
+  "Your Username": "Το όνομα χρήστη σας",
+  "Password": "Κωδικός πρόσβασης",
+  "Connect": "Σύνδεση",
+  "KOReader Sync": "Συγχρονισμός KOReader",
+  "Sync Conflict": "Σύγκρουση συγχρονισμού",
+  "Sync reading progress from \"{{deviceName}}\"?": "Συγχρονίστε την πρόοδο ανάγνωσης από το \"{{deviceName}}\";",
+  "another device": "άλλη συσκευή",
+  "Local Progress": "Τοπική πρόοδος",
+  "Remote Progress": "Απομακρυσμένη πρόοδος",
+  "Page {{page}} of {{total}} ({{percentage}}%)": "Σελίδα {{page}} από {{total}} ({{percentage}}%)",
+  "Current position": "Τρέχουσα θέση",
+  "Approximately page {{page}} of {{total}} ({{percentage}}%)": "Περίπου σελίδα {{page}} από {{total}} ({{percentage}}%)",
+  "Approximately {{percentage}}%": "Περίπου {{percentage}}%"
 }
diff --git a/apps/readest-app/public/locales/es/translation.json b/apps/readest-app/public/locales/es/translation.json
index 655d5883..0037a4f6 100644
--- a/apps/readest-app/public/locales/es/translation.json
+++ b/apps/readest-app/public/locales/es/translation.json
@@ -69,7 +69,40 @@
   "Parallel Read": "Lectura paralela",
   "Published": "Publicado",
   "Publisher": "Editorial",
+  "KOReader Sync": "Sincronización con KOReader",
+  "KOReader Sync Settings": "Ajustes de Sincronización con KOReader",
+  "Your Username": "Tu nombre de usuario",
+  "Connect to your KOReader Sync server.": "Conéctate a tu servidor de KOReader Sync.",
+  "Connected as {{username}}": "Conectado como {{username}}",
+  "Server URL": "URL del Servidor",
+  "Username": "Usuario",
+  "Password": "Contraseña",
+  "Connect": "Conectar",
+  "Disconnect": "Desconectar",
+  "Disconnected": "Desconectado",
+  "Error": "Error",
+  "Sync Strategy": "Estrategia de sincronización",
+  "Ask on conflict": "Preguntar en caso de conflicto",
+  "Always use latest": "Usar siempre el más reciente",
+  "Send changes only": "Solo enviar cambios",
+  "Receive changes only": "Solo recibir cambios",
+  "Disabled": "Desactivado",
+  "Checksum Method": "Método de identificación",
+  "File Content (recommended)": "Contenido del archivo (recomendado)",
+  "File Name": "Nombre del archivo",
+  "Device Name": "Nombre del dispositivo",
+  "Sync Tolerance": "Tolerancia de sincronización",
+  "Precision: {{precision}} decimal places": "Precisión: {{precision}} decimales",
   "Reading Progress Synced": "Progreso de lectura sincronizado",
+  "Sync Conflict": "Conflicto de sincronización",
+  "Sync reading progress from \"{{deviceName}}\"?": "¿Quieres sincronizar el progreso de lectura desde el dispositivo \"{{deviceName}}\"?",
+  "Local Progress": "Progreso local",
+  "Remote Progress": "Progreso remoto",
+  "Page {{page}} of {{total}} ({{percentage}}%)": "Página {{page}} de {{total}} ({{percentage}}%)",
+  "Approximately page {{page}} of {{total}} ({{percentage}}%)": "Aproximadamente página {{page}} de {{total}} ({{percentage}}%)",
+  "Current position": "Posición actual",
+  "Approximately {{percentage}}%": "Aproximadamente {{percentage}}%",
+  "another device": "otro dispositivo",
   "Reload Page": "Recargar página",
   "Reveal in File Explorer": "Mostrar en el Explorador de archivos",
   "Reveal in Finder": "Mostrar en Finder",
diff --git a/apps/readest-app/public/locales/fr/translation.json b/apps/readest-app/public/locales/fr/translation.json
index 96ea291f..5e8692eb 100644
--- a/apps/readest-app/public/locales/fr/translation.json
+++ b/apps/readest-app/public/locales/fr/translation.json
@@ -475,5 +475,38 @@
   "Are you sure to delete the local copy of the selected book?": "Êtes-vous sûr de vouloir supprimer la copie locale du livre sélectionné ?",
   "Remove from Cloud & Device": "Supprimer du Cloud & de l'appareil",
   "Remove from Cloud Only": "Supprimer uniquement du Cloud",
-  "Remove from Device Only": "Supprimer uniquement de l'appareil"
+  "Remove from Device Only": "Supprimer uniquement de l'appareil",
+  "Error": "Erreur",
+  "Disconnected": "Déconnecté",
+  "KOReader Sync Settings": "Paramètres de synchronisation KOReader",
+  "Connected as {{username}}": "Connecté en tant que {{username}}",
+  "Disconnect": "Déconnecter",
+  "Sync Strategy": "Stratégie de synchronisation",
+  "Ask on conflict": "Demander en cas de conflit",
+  "Always use latest": "Toujours utiliser la dernière version",
+  "Send changes only": "Envoyer uniquement les modifications",
+  "Receive changes only": "Recevoir uniquement les modifications",
+  "Disabled": "Désactivé",
+  "Checksum Method": "Méthode de somme de contrôle",
+  "File Content (recommended)": "Contenu du fichier (recommandé)",
+  "File Name": "Nom du fichier",
+  "Device Name": "Nom de l'appareil",
+  "Sync Tolerance": "Tolérance de synchronisation",
+  "Precision: {{precision}} decimal places": "Précision : {{precision}} décimales",
+  "Connect to your KOReader Sync server.": "Connectez-vous à votre serveur de synchronisation KOReader.",
+  "Server URL": "URL du serveur",
+  "Username": "Nom d'utilisateur",
+  "Your Username": "Votre nom d'utilisateur",
+  "Password": "Mot de passe",
+  "Connect": "Connecter",
+  "KOReader Sync": "Synchronisation KOReader",
+  "Sync Conflict": "Conflit de synchronisation",
+  "Sync reading progress from \"{{deviceName}}\"?": "Synchroniser la progression de lecture depuis \"{{deviceName}}\"?",
+  "another device": "un autre appareil",
+  "Local Progress": "Progression locale",
+  "Remote Progress": "Progression distante",
+  "Page {{page}} of {{total}} ({{percentage}}%)": "Page {{page}} sur {{total}} ({{percentage}}%)",
+  "Current position": "Position actuelle",
+  "Approximately page {{page}} of {{total}} ({{percentage}}%)": "Environ page {{page}} sur {{total}} ({{percentage}}%)",
+  "Approximately {{percentage}}%": "Environ {{percentage}}%"
 }
diff --git a/apps/readest-app/public/locales/hi/translation.json b/apps/readest-app/public/locales/hi/translation.json
index 4ba73eae..ee2dc7f4 100644
--- a/apps/readest-app/public/locales/hi/translation.json
+++ b/apps/readest-app/public/locales/hi/translation.json
@@ -471,5 +471,38 @@
   "Are you sure to delete the local copy of the selected book?": "क्या आप सुनिश्चित हैं कि आप चयनित पुस्तक की स्थानीय प्रति हटाना चाहते हैं?",
   "Remove from Cloud & Device": "क्लाउड और डिवाइस से हटाएँ",
   "Remove from Cloud Only": "केवल क्लाउड से हटाएँ",
-  "Remove from Device Only": "केवल डिवाइस से हटाएँ"
+  "Remove from Device Only": "केवल डिवाइस से हटाएँ",
+  "Error": "त्रुटि",
+  "Disconnected": "अविचलित",
+  "KOReader Sync Settings": "KOReader सिंक सेटिंग्स",
+  "Connected as {{username}}": "जुड़ा हुआ {{username}} के रूप में",
+  "Disconnect": "अविचलित करें",
+  "Sync Strategy": "सिंक रणनीति",
+  "Ask on conflict": "संघर्ष पर पूछें",
+  "Always use latest": "हमेशा नवीनतम का उपयोग करें",
+  "Send changes only": "केवल परिवर्तन भेजें",
+  "Receive changes only": "केवल परिवर्तन प्राप्त करें",
+  "Disabled": "अक्षम",
+  "Checksum Method": "चेकसम विधि",
+  "File Content (recommended)": "फाइल सामग्री (अनुशंसित)",
+  "File Name": "फाइल नाम",
+  "Device Name": "डिवाइस नाम",
+  "Sync Tolerance": "सिंक सहिष्णुता",
+  "Precision: {{precision}} decimal places": "सटीकता: {{precision}} दशमलव स्थान",
+  "Connect to your KOReader Sync server.": "अपने KOReader सिंक सर्वर से कनेक्ट करें।",
+  "Server URL": "सर्वर यूआरएल",
+  "Username": "उपयोगकर्ता नाम",
+  "Your Username": "आपका उपयोगकर्ता नाम",
+  "Password": "पासवर्ड",
+  "Connect": "कनेक्ट करें",
+  "KOReader Sync": "KOReader सिंक",
+  "Sync Conflict": "सिंक संघर्ष",
+  "Sync reading progress from \"{{deviceName}}\"?": "क्या आप \"{{deviceName}}\" से पढ़ने की प्रगति को सिंक करना चाहते हैं?",
+  "another device": "दूसरा डिवाइस",
+  "Local Progress": "स्थानीय प्रगति",
+  "Remote Progress": "दूरस्थ प्रगति",
+  "Page {{page}} of {{total}} ({{percentage}}%)": "पृष्ठ {{page}} कुल {{total}} ({{percentage}}%)",
+  "Current position": "वर्तमान स्थिति",
+  "Approximately page {{page}} of {{total}} ({{percentage}}%)": "लगभग पृष्ठ {{page}} कुल {{total}} ({{percentage}}%)",
+  "Approximately {{percentage}}%": "लगभग {{percentage}}%"
 }
diff --git a/apps/readest-app/public/locales/id/translation.json b/apps/readest-app/public/locales/id/translation.json
index 9af875ee..39dd0605 100644
--- a/apps/readest-app/public/locales/id/translation.json
+++ b/apps/readest-app/public/locales/id/translation.json
@@ -462,11 +462,43 @@
   "Page Number": "Nomor Halaman",
   "Percentage": "Persentase",
   "Deleted local copy of the book: {{title}}": "Salinan lokal buku dihapus: {{title}}",
-
   "Failed to delete cloud backup of the book: {{title}}": "Gagal menghapus cadangan cloud buku: {{title}}",
   "Failed to delete local copy of the book: {{title}}": "Gagal menghapus salinan lokal buku: {{title}}",
   "Are you sure to delete the local copy of the selected book?": "Apakah Anda yakin ingin menghapus salinan lokal buku yang dipilih?",
   "Remove from Cloud & Device": "Hapus dari Cloud & Perangkat",
   "Remove from Cloud Only": "Hapus dari Cloud Saja",
-  "Remove from Device Only": "Hapus dari Perangkat Saja"
+  "Remove from Device Only": "Hapus dari Perangkat Saja",
+  "Error": "Kesalahan",
+  "Disconnected": "Terputus",
+  "KOReader Sync Settings": "Pengaturan Sinkronisasi KOReader",
+  "Connected as {{username}}": "Terhubung sebagai {{username}}",
+  "Disconnect": "Putuskan Koneksi",
+  "Sync Strategy": "Strategi Sinkronisasi",
+  "Ask on conflict": "Tanya saat terjadi konflik",
+  "Always use latest": "Selalu gunakan yang terbaru",
+  "Send changes only": "Kirim perubahan saja",
+  "Receive changes only": "Terima perubahan saja",
+  "Disabled": "Dinonaktifkan",
+  "Checksum Method": "Metode Checksum",
+  "File Content (recommended)": "Konten File (disarankan)",
+  "File Name": "Nama File",
+  "Device Name": "Nama Perangkat",
+  "Sync Tolerance": "Toleransi Sinkronisasi",
+  "Precision: {{precision}} decimal places": "Presisi: {{precision}} tempat desimal",
+  "Connect to your KOReader Sync server.": "Hubungkan ke server Sinkronisasi KOReader Anda.",
+  "Server URL": "URL Server",
+  "Username": "Nama Pengguna",
+  "Your Username": "Nama Pengguna Anda",
+  "Password": "Kata Sandi",
+  "Connect": "Hubungkan",
+  "KOReader Sync": "Sinkronisasi KOReader",
+  "Sync Conflict": "Konflik Sinkronisasi",
+  "Sync reading progress from \"{{deviceName}}\"?": "Sinkronkan progres membaca dari \"{{deviceName}}\"?",
+  "another device": "perangkat lain",
+  "Local Progress": "Progres Lokal",
+  "Remote Progress": "Progres Jarak Jauh",
+  "Page {{page}} of {{total}} ({{percentage}}%)": "Halaman {{page}} dari {{total}} ({{percentage}}%)",
+  "Current position": "Posisi Saat Ini",
+  "Approximately page {{page}} of {{total}} ({{percentage}}%)": "Sekitar halaman {{page}} dari {{total}} ({{percentage}}%)",
+  "Approximately {{percentage}}%": "Sekitar {{percentage}}%"
 }
diff --git a/apps/readest-app/public/locales/it/translation.json b/apps/readest-app/public/locales/it/translation.json
index fc58199e..efe0925d 100644
--- a/apps/readest-app/public/locales/it/translation.json
+++ b/apps/readest-app/public/locales/it/translation.json
@@ -475,5 +475,38 @@
   "Are you sure to delete the local copy of the selected book?": "Sei sicuro di voler eliminare la copia locale del libro selezionato?",
   "Remove from Cloud & Device": "Rimuovi da Cloud & Dispositivo",
   "Remove from Cloud Only": "Rimuovi solo da Cloud",
-  "Remove from Device Only": "Rimuovi solo da Dispositivo"
+  "Remove from Device Only": "Rimuovi solo da Dispositivo",
+  "Error": "Errore",
+  "Disconnected": "Disconnesso",
+  "KOReader Sync Settings": "Impostazioni di Sincronizzazione KOReader",
+  "Connected as {{username}}": "Connesso come {{username}}",
+  "Disconnect": "Disconnetti",
+  "Sync Strategy": "Strategia di Sincronizzazione",
+  "Ask on conflict": "Chiedi in caso di conflitto",
+  "Always use latest": "Usa sempre l'ultima versione",
+  "Send changes only": "Invia solo le modifiche",
+  "Receive changes only": "Ricevi solo le modifiche",
+  "Disabled": "Disabilitato",
+  "Checksum Method": "Metodo di Controllo",
+  "File Content (recommended)": "Contenuto del File (consigliato)",
+  "File Name": "Nome del File",
+  "Device Name": "Nome del Dispositivo",
+  "Sync Tolerance": "Tolleranza di Sincronizzazione",
+  "Precision: {{precision}} decimal places": "Precisione: {{precision}} posizioni decimali",
+  "Connect to your KOReader Sync server.": "Connettiti al tuo server KOReader Sync.",
+  "Server URL": "URL del Server",
+  "Username": "Nome Utente",
+  "Your Username": "Il tuo Nome Utente",
+  "Password": "Password",
+  "Connect": "Connetti",
+  "KOReader Sync": "KOReader Sync",
+  "Sync Conflict": "Conflitto di Sincronizzazione",
+  "Sync reading progress from \"{{deviceName}}\"?": "Sincronizzare il progresso di lettura da \"{{deviceName}}\"?",
+  "another device": "un altro dispositivo",
+  "Local Progress": "Progresso Locale",
+  "Remote Progress": "Progresso Remoto",
+  "Page {{page}} of {{total}} ({{percentage}}%)": "Pagina {{page}} di {{total}} ({{percentage}}%)",
+  "Current position": "Posizione Corrente",
+  "Approximately page {{page}} of {{total}} ({{percentage}}%)": "Circa pagina {{page}} di {{total}} ({{percentage}}%)",
+  "Approximately {{percentage}}%": "Circa {{percentage}}%"
 }
diff --git a/apps/readest-app/public/locales/ja/translation.json b/apps/readest-app/public/locales/ja/translation.json
index d831cfa4..3ea5be7f 100644
--- a/apps/readest-app/public/locales/ja/translation.json
+++ b/apps/readest-app/public/locales/ja/translation.json
@@ -467,5 +467,38 @@
   "Are you sure to delete the local copy of the selected book?": "選択した書籍のローカルコピーを削除してもよろしいですか？",
   "Remove from Cloud & Device": "クラウドとデバイスから削除",
   "Remove from Cloud Only": "クラウドからのみ削除",
-  "Remove from Device Only": "デバイスからのみ削除"
+  "Remove from Device Only": "デバイスからのみ削除",
+  "Error": "エラー",
+  "Disconnected": "切断されました",
+  "KOReader Sync Settings": "KOReader Sync設定",
+  "Connected as {{username}}": "{{username}}として接続されています",
+  "Disconnect": "切断",
+  "Sync Strategy": "同期戦略",
+  "Ask on conflict": "競合時に確認",
+  "Always use latest": "最新を常に使用",
+  "Send changes only": "変更のみを送信",
+  "Receive changes only": "変更のみを受信",
+  "Disabled": "無効",
+  "Checksum Method": "チェックサム方式",
+  "File Content (recommended)": "ファイル内容（推奨）",
+  "File Name": "ファイル名",
+  "Device Name": "デバイス名",
+  "Sync Tolerance": "同期許容範囲",
+  "Precision: {{precision}} decimal places": "精度: {{precision}} 小数点以下",
+  "Connect to your KOReader Sync server.": "KOReader Syncサーバーに接続します。",
+  "Server URL": "サーバーURL",
+  "Username": "ユーザー名",
+  "Your Username": "あなたのユーザー名",
+  "Password": "パスワード",
+  "Connect": "接続",
+  "KOReader Sync": "KOReader Sync",
+  "Sync Conflict": "同期競合",
+  "Sync reading progress from \"{{deviceName}}\"?": "{{deviceName}}から読書進捗を同期しますか？",
+  "another device": "別のデバイス",
+  "Local Progress": "ローカル進捗",
+  "Remote Progress": "リモート進捗",
+  "Page {{page}} of {{total}} ({{percentage}}%)": "ページ {{page}} / {{total}} ({{percentage}}%)",
+  "Current position": "現在の位置",
+  "Approximately page {{page}} of {{total}} ({{percentage}}%)": "おおよそページ {{page}} / {{total}} ({{percentage}}%)",
+  "Approximately {{percentage}}%": "おおよそ {{percentage}}%"
 }
diff --git a/apps/readest-app/public/locales/ko/translation.json b/apps/readest-app/public/locales/ko/translation.json
index 470ae7f8..194d2eac 100644
--- a/apps/readest-app/public/locales/ko/translation.json
+++ b/apps/readest-app/public/locales/ko/translation.json
@@ -467,5 +467,38 @@
   "Are you sure to delete the local copy of the selected book?": "선택한 책의 로컬 사본을 삭제하시겠습니까?",
   "Remove from Cloud & Device": "클라우드 및 장치에서 제거",
   "Remove from Cloud Only": "클라우드에서만 제거",
-  "Remove from Device Only": "장치에서만 제거"
+  "Remove from Device Only": "장치에서만 제거",
+  "Error": "오류",
+  "Disconnected": "연결 끊김",
+  "KOReader Sync Settings": "KOReader Sync 설정",
+  "Connected as {{username}}": "{{username}}로 연결됨",
+  "Disconnect": "연결 끊기",
+  "Sync Strategy": "동기화 전략",
+  "Ask on conflict": "충돌 시 묻기",
+  "Always use latest": "항상 최신 버전 사용",
+  "Send changes only": "변경 사항만 전송",
+  "Receive changes only": "변경 사항만 수신",
+  "Disabled": "비활성화",
+  "Checksum Method": "체크섬 방법",
+  "File Content (recommended)": "파일 내용 (권장)",
+  "File Name": "파일 이름",
+  "Device Name": "장치 이름",
+  "Sync Tolerance": "동기화 허용 오차",
+  "Precision: {{precision}} decimal places": "정밀도: {{precision}} 소수 자리",
+  "Connect to your KOReader Sync server.": "KOReader Sync 서버에 연결합니다.",
+  "Server URL": "서버 URL",
+  "Username": "사용자 이름",
+  "Your Username": "당신의 사용자 이름",
+  "Password": "비밀번호",
+  "Connect": "연결",
+  "KOReader Sync": "KOReader Sync",
+  "Sync Conflict": "동기화 충돌",
+  "Sync reading progress from \"{{deviceName}}\"?": " \"{{deviceName}}\"에서 읽기 진행 상황을 동기화하시겠습니까?",
+  "another device": "다른 장치",
+  "Local Progress": "로컬 진행 상황",
+  "Remote Progress": "원격 진행 상황",
+  "Page {{page}} of {{total}} ({{percentage}}%)": "페이지 {{page}} / {{total}} ({{percentage}}%)",
+  "Current position": "현재 위치",
+  "Approximately page {{page}} of {{total}} ({{percentage}}%)": "대략 페이지 {{page}} / {{total}} ({{percentage}}%)",
+  "Approximately {{percentage}}%": "대략 {{percentage}}%"
 }
diff --git a/apps/readest-app/public/locales/nl/translation.json b/apps/readest-app/public/locales/nl/translation.json
index 310ab8c0..9c249696 100644
--- a/apps/readest-app/public/locales/nl/translation.json
+++ b/apps/readest-app/public/locales/nl/translation.json
@@ -471,5 +471,38 @@
   "Are you sure to delete the local copy of the selected book?": "Weet je zeker dat je de lokale kopie van het geselecteerde boek wilt verwijderen?",
   "Remove from Cloud & Device": "Verwijder uit Cloud & Apparaat",
   "Remove from Cloud Only": "Verwijder alleen uit Cloud",
-  "Remove from Device Only": "Verwijder alleen uit Apparaat"
+  "Remove from Device Only": "Verwijder alleen uit Apparaat",
+  "Error": "Fout",
+  "Disconnected": "Verbroken",
+  "KOReader Sync Settings": "KOReader Sync-instellingen",
+  "Connected as {{username}}": "Verbonden als {{username}}",
+  "Disconnect": "Verbreken",
+  "Sync Strategy": "Synchronisatiestrategie",
+  "Ask on conflict": "Vraag bij conflict",
+  "Always use latest": "Altijd de nieuwste gebruiken",
+  "Send changes only": "Verzend alleen wijzigingen",
+  "Receive changes only": "Ontvang alleen wijzigingen",
+  "Disabled": "Uitgeschakeld",
+  "Checksum Method": "Checksum-methode",
+  "File Content (recommended)": "Bestandsinhoud (aanbevolen)",
+  "File Name": "Bestandsnaam",
+  "Device Name": "Apparaatnaam",
+  "Sync Tolerance": "Synchronisatietolerantie",
+  "Precision: {{precision}} decimal places": "Precisie: {{precision}} decimalen",
+  "Connect to your KOReader Sync server.": "Verbind met je KOReader Sync-server.",
+  "Server URL": "Server-URL",
+  "Username": "Gebruikersnaam",
+  "Your Username": "Je gebruikersnaam",
+  "Password": "Wachtwoord",
+  "Connect": "Verbinden",
+  "KOReader Sync": "KOReader Sync",
+  "Sync Conflict": "Synchronisatieconflict",
+  "Sync reading progress from \"{{deviceName}}\"?": "Leesvoortgang synchroniseren van \"{{deviceName}}\"?",
+  "another device": "een ander apparaat",
+  "Local Progress": "Lokale voortgang",
+  "Remote Progress": "Externe voortgang",
+  "Page {{page}} of {{total}} ({{percentage}}%)": "Pagina {{page}} van {{total}} ({{percentage}}%)",
+  "Current position": "Huidige positie",
+  "Approximately page {{page}} of {{total}} ({{percentage}}%)": "Ongeveer pagina {{page}} van {{total}} ({{percentage}}%)",
+  "Approximately {{percentage}}%": "Ongeveer {{percentage}}%"
 }
diff --git a/apps/readest-app/public/locales/pl/translation.json b/apps/readest-app/public/locales/pl/translation.json
index 3976ea53..ecd97232 100644
--- a/apps/readest-app/public/locales/pl/translation.json
+++ b/apps/readest-app/public/locales/pl/translation.json
@@ -479,5 +479,38 @@
   "Are you sure to delete the local copy of the selected book?": "Czy na pewno chcesz usunąć lokalną kopię wybranej książki?",
   "Remove from Cloud & Device": "Usuń z chmury i urządzenia",
   "Remove from Cloud Only": "Usuń tylko z chmury",
-  "Remove from Device Only": "Usuń tylko z urządzenia"
+  "Remove from Device Only": "Usuń tylko z urządzenia",
+  "Error": "Błąd",
+  "Disconnected": "Rozłączono",
+  "KOReader Sync Settings": "Ustawienia synchronizacji KOReader",
+  "Connected as {{username}}": "Połączono jako {{username}}",
+  "Disconnect": "Rozłącz",
+  "Sync Strategy": "Strategia synchronizacji",
+  "Ask on conflict": "Pytaj w przypadku konfliktu",
+  "Always use latest": "Zawsze używaj najnowszej",
+  "Send changes only": "Wyślij tylko zmiany",
+  "Receive changes only": "Odbierz tylko zmiany",
+  "Disabled": "Wyłączone",
+  "Checksum Method": "Metoda sumy kontrolnej",
+  "File Content (recommended)": "Zawartość pliku (zalecane)",
+  "File Name": "Nazwa pliku",
+  "Device Name": "Nazwa urządzenia",
+  "Sync Tolerance": "Tolerancja synchronizacji",
+  "Precision: {{precision}} decimal places": "Precyzja: {{precision}} miejsc po przecinku",
+  "Connect to your KOReader Sync server.": "Połącz z serwerem synchronizacji KOReader.",
+  "Server URL": "Adres URL serwera",
+  "Username": "Nazwa użytkownika",
+  "Your Username": "Twoja nazwa użytkownika",
+  "Password": "Hasło",
+  "Connect": "Połącz",
+  "KOReader Sync": "Synchronizacja KOReader",
+  "Sync Conflict": "Konflikt synchronizacji",
+  "Sync reading progress from \"{{deviceName}}\"?": "Synchronizować postęp czytania z \"{{deviceName}}\"?",
+  "another device": "inne urządzenie",
+  "Local Progress": "Postęp lokalny",
+  "Remote Progress": "Postęp zdalny",
+  "Page {{page}} of {{total}} ({{percentage}}%)": "Strona {{page}} z {{total}} ({{percentage}}%)",
+  "Current position": "Bieżąca pozycja",
+  "Approximately page {{page}} of {{total}} ({{percentage}}%)": "Około strona {{page}} z {{total}} ({{percentage}}%)",
+  "Approximately {{percentage}}%": "Około {{percentage}}%"
 }
diff --git a/apps/readest-app/public/locales/pt/translation.json b/apps/readest-app/public/locales/pt/translation.json
index c475c9ec..9022bb13 100644
--- a/apps/readest-app/public/locales/pt/translation.json
+++ b/apps/readest-app/public/locales/pt/translation.json
@@ -475,5 +475,38 @@
   "Are you sure to delete the local copy of the selected book?": "Tem certeza de que deseja excluir a cópia local do livro selecionado?",
   "Remove from Cloud & Device": "Remover da Nuvem & Dispositivo",
   "Remove from Cloud Only": "Remover apenas da Nuvem",
-  "Remove from Device Only": "Remover apenas do Dispositivo"
+  "Remove from Device Only": "Remover apenas do Dispositivo",
+  "Error": "Erro",
+  "Disconnected": "Desconectado",
+  "KOReader Sync Settings": "Configurações de Sincronização KOReader",
+  "Connected as {{username}}": "Conectado como {{username}}",
+  "Disconnect": "Desconectar",
+  "Sync Strategy": "Estratégia de Sincronização",
+  "Ask on conflict": "Perguntar em caso de conflito",
+  "Always use latest": "Sempre usar o mais recente",
+  "Send changes only": "Enviar apenas alterações",
+  "Receive changes only": "Receber apenas alterações",
+  "Disabled": "Desativado",
+  "Checksum Method": "Método de Verificação",
+  "File Content (recommended)": "Conteúdo do Arquivo (recomendado)",
+  "File Name": "Nome do Arquivo",
+  "Device Name": "Nome do Dispositivo",
+  "Sync Tolerance": "Tolerância de Sincronização",
+  "Precision: {{precision}} decimal places": "Precisão: {{precision}} casas decimais",
+  "Connect to your KOReader Sync server.": "Conectar ao seu servidor KOReader Sync.",
+  "Server URL": "URL do Servidor",
+  "Username": "Nome de Usuário",
+  "Your Username": "Seu Nome de Usuário",
+  "Password": "Senha",
+  "Connect": "Conectar",
+  "KOReader Sync": "KOReader Sync",
+  "Sync Conflict": "Conflito de Sincronização",
+  "Sync reading progress from \"{{deviceName}}\"?": "Sincronizar progresso de leitura de \"{{deviceName}}\"?",
+  "another device": "outro dispositivo",
+  "Local Progress": "Progresso Local",
+  "Remote Progress": "Progresso Remoto",
+  "Page {{page}} of {{total}} ({{percentage}}%)": "Página {{page}} de {{total}} ({{percentage}}%)",
+  "Current position": "Posição Atual",
+  "Approximately page {{page}} of {{total}} ({{percentage}}%)": "Aproximadamente página {{page}} de {{total}} ({{percentage}}%)",
+  "Approximately {{percentage}}%": "Aproximadamente {{percentage}}%"
 }
diff --git a/apps/readest-app/public/locales/ru/translation.json b/apps/readest-app/public/locales/ru/translation.json
index 20788a43..cb57d3c3 100644
--- a/apps/readest-app/public/locales/ru/translation.json
+++ b/apps/readest-app/public/locales/ru/translation.json
@@ -479,5 +479,38 @@
   "Are you sure to delete the local copy of the selected book?": "Вы уверены, что хотите удалить локальную копию выбранной книги?",
   "Remove from Cloud & Device": "Удалить из облака и устройства",
   "Remove from Cloud Only": "Удалить только из облака",
-  "Remove from Device Only": "Удалить только с устройства"
+  "Remove from Device Only": "Удалить только с устройства",
+  "Error": "Ошибка",
+  "Disconnected": "Отключено",
+  "KOReader Sync Settings": "Настройки синхронизации KOReader",
+  "Connected as {{username}}": "Подключено как {{username}}",
+  "Disconnect": "Отключить",
+  "Sync Strategy": "Стратегия синхронизации",
+  "Ask on conflict": "Спрашивать при конфликте",
+  "Always use latest": "Всегда использовать последнюю",
+  "Send changes only": "Отправлять только изменения",
+  "Receive changes only": "Получать только изменения",
+  "Disabled": "Отключено",
+  "Checksum Method": "Метод контрольной суммы",
+  "File Content (recommended)": "Содержимое файла (рекомендуется)",
+  "File Name": "Имя файла",
+  "Device Name": "Имя устройства",
+  "Sync Tolerance": "Допуск синхронизации",
+  "Precision: {{precision}} decimal places": "Точность: {{precision}} десятичных знаков",
+  "Connect to your KOReader Sync server.": "Подключитесь к вашему серверу синхронизации KOReader.",
+  "Server URL": "URL сервера",
+  "Username": "Имя пользователя",
+  "Your Username": "Ваше имя пользователя",
+  "Password": "Пароль",
+  "Connect": "Подключиться",
+  "KOReader Sync": "KOReader Sync",
+  "Sync Conflict": "Конфликт синхронизации",
+  "Sync reading progress from \"{{deviceName}}\"?": "Синхронизировать прогресс чтения с \"{{deviceName}}\"?",
+  "another device": "другом устройстве",
+  "Local Progress": "Локальный прогресс",
+  "Remote Progress": "Удаленный прогресс",
+  "Page {{page}} of {{total}} ({{percentage}}%)": "Страница {{page}} из {{total}} ({{percentage}}%)",
+  "Current position": "Текущая позиция",
+  "Approximately page {{page}} of {{total}} ({{percentage}}%)": "Приблизительно страница {{page}} из {{total}} ({{percentage}}%)",
+  "Approximately {{percentage}}%": "Приблизительно {{percentage}}%"
 }
diff --git a/apps/readest-app/public/locales/th/translation.json b/apps/readest-app/public/locales/th/translation.json
index 5b4cdf19..5bb6cb95 100644
--- a/apps/readest-app/public/locales/th/translation.json
+++ b/apps/readest-app/public/locales/th/translation.json
@@ -467,5 +467,38 @@
   "Are you sure to delete the local copy of the selected book?": "คุณแน่ใจหรือไม่ว่าต้องการลบสำเนาในเครื่องของหนังสือที่เลือก?",
   "Remove from Cloud & Device": "ลบจากคลาวด์และอุปกรณ์",
   "Remove from Cloud Only": "ลบจากคลาวด์เท่านั้น",
-  "Remove from Device Only": "ลบจากอุปกรณ์เท่านั้น"
+  "Remove from Device Only": "ลบจากอุปกรณ์เท่านั้น",
+  "Error": "เกิดข้อผิดพลาด",
+  "Disconnected": "ตัดการเชื่อมต่อ",
+  "KOReader Sync Settings": "การตั้งค่าการซิงค์ KOReader",
+  "Connected as {{username}}": "เชื่อมต่อเป็น {{username}}",
+  "Disconnect": "ตัดการเชื่อมต่อ",
+  "Sync Strategy": "กลยุทธ์การซิงค์",
+  "Ask on conflict": "ถามเมื่อเกิดความขัดแย้ง",
+  "Always use latest": "ใช้เวอร์ชันล่าสุดเสมอ",
+  "Send changes only": "ส่งการเปลี่ยนแปลงเท่านั้น",
+  "Receive changes only": "รับการเปลี่ยนแปลงเท่านั้น",
+  "Disabled": "ปิดใช้งาน",
+  "Checksum Method": "วิธีการตรวจสอบความถูกต้อง",
+  "File Content (recommended)": "เนื้อหาไฟล์ (แนะนำ)",
+  "File Name": "ชื่อไฟล์",
+  "Device Name": "ชื่ออุปกรณ์",
+  "Sync Tolerance": "ความทนทานต่อการซิงค์",
+  "Precision: {{precision}} decimal places": "ความแม่นยำ: {{precision}} ตำแหน่งทศนิยม",
+  "Connect to your KOReader Sync server.": "เชื่อมต่อกับเซิร์ฟเวอร์ KOReader Sync ของคุณ",
+  "Server URL": "URL ของเซิร์ฟเวอร์",
+  "Username": "ชื่อผู้ใช้",
+  "Your Username": "ชื่อผู้ใช้ของคุณ",
+  "Password": "รหัสผ่าน",
+  "Connect": "เชื่อมต่อ",
+  "KOReader Sync": "KOReader Sync",
+  "Sync Conflict": "ความขัดแย้งในการซิงค์",
+  "Sync reading progress from \"{{deviceName}}\"?": "ซิงค์ความก้าวหน้าในการอ่านจาก \"{{deviceName}}\"?",
+  "another device": "อุปกรณ์อื่น",
+  "Local Progress": "ความก้าวหน้าในเครื่อง",
+  "Remote Progress": "ความก้าวหน้าในคลาวด์",
+  "Page {{page}} of {{total}} ({{percentage}}%)": "หน้า {{page}} จาก {{total}} ({{percentage}}%)",
+  "Current position": "ตำแหน่งปัจจุบัน",
+  "Approximately page {{page}} of {{total}} ({{percentage}}%)": "ประมาณหน้า {{page}} จาก {{total}} ({{percentage}}%)",
+  "Approximately {{percentage}}%": "ประมาณ {{percentage}}%"
 }
diff --git a/apps/readest-app/public/locales/tr/translation.json b/apps/readest-app/public/locales/tr/translation.json
index d4cd2d5a..84d16130 100644
--- a/apps/readest-app/public/locales/tr/translation.json
+++ b/apps/readest-app/public/locales/tr/translation.json
@@ -471,5 +471,38 @@
   "Are you sure to delete the local copy of the selected book?": "Seçilen kitabın yerel kopyasını silmek istediğinize emin misiniz?",
   "Remove from Cloud & Device": "Buluttan ve Cihazdan Kaldır",
   "Remove from Cloud Only": "Sadece Buluttan Kaldır",
-  "Remove from Device Only": "Sadece Cihazdan Kaldır"
+  "Remove from Device Only": "Sadece Cihazdan Kaldır",
+  "Error": "Hata",
+  "Disconnected": "Bağlantı Kesildi",
+  "KOReader Sync Settings": "KOReader Senkronizasyon Ayarları",
+  "Connected as {{username}}": "{{username}} olarak bağlandı",
+  "Disconnect": "Bağlantıyı Kes",
+  "Sync Strategy": "Senkronizasyon Stratejisi",
+  "Ask on conflict": "Çatışmada Sor",
+  "Always use latest": "Her Zaman En Sonunu Kullan",
+  "Send changes only": "Sadece Değişiklikleri Gönder",
+  "Receive changes only": "Sadece Değişiklikleri Al",
+  "Disabled": "Devre Dışı",
+  "Checksum Method": "Kontrol Toplamı Yöntemi",
+  "File Content (recommended)": "Dosya İçeriği (önerilen)",
+  "File Name": "Dosya Adı",
+  "Device Name": "Cihaz Adı",
+  "Sync Tolerance": "Senkronizasyon Toleransı",
+  "Precision: {{precision}} decimal places": "Hassasiyet: {{precision}} ondalık basamak",
+  "Connect to your KOReader Sync server.": "KOReader Senkronizasyon sunucunuza bağlanın.",
+  "Server URL": "Sunucu URL'si",
+  "Username": "Kullanıcı Adı",
+  "Your Username": "Kullanıcı Adınız",
+  "Password": "Şifre",
+  "Connect": "Bağlan",
+  "KOReader Sync": "KOReader Senkronizasyon",
+  "Sync Conflict": "Senkronizasyon Çatışması",
+  "Sync reading progress from \"{{deviceName}}\"?": "\"{{deviceName}}\" cihazından okuma ilerlemesini senkronize etmek istiyor musunuz?",
+  "another device": "başka bir cihaz",
+  "Local Progress": "Yerel İlerleme",
+  "Remote Progress": "Uzak İlerleme",
+  "Page {{page}} of {{total}} ({{percentage}}%)": "Sayfa {{page}} / {{total}} ({{percentage}}%)",
+  "Current position": "Mevcut konum",
+  "Approximately page {{page}} of {{total}} ({{percentage}}%)": "Yaklaşık sayfa {{page}} / {{total}} ({{percentage}}%)",
+  "Approximately {{percentage}}%": "Yaklaşık {{percentage}}%"
 }
diff --git a/apps/readest-app/public/locales/uk/translation.json b/apps/readest-app/public/locales/uk/translation.json
index 9f24d1b1..7f1e041a 100644
--- a/apps/readest-app/public/locales/uk/translation.json
+++ b/apps/readest-app/public/locales/uk/translation.json
@@ -479,5 +479,38 @@
   "Are you sure to delete the local copy of the selected book?": "Ви впевнені, що хочете видалити локальну копію вибраної книги?",
   "Remove from Cloud & Device": "Видалити з хмари та пристрою",
   "Remove from Cloud Only": "Видалити тільки з хмари",
-  "Remove from Device Only": "Видалити тільки з пристрою"
+  "Remove from Device Only": "Видалити тільки з пристрою",
+  "Error": "Помилка",
+  "Disconnected": "Відключено",
+  "KOReader Sync Settings": "Налаштування синхронізації KOReader",
+  "Connected as {{username}}": "Підключено як {{username}}",
+  "Disconnect": "Відключити",
+  "Sync Strategy": "Стратегія синхронізації",
+  "Ask on conflict": "Запитувати при конфлікті",
+  "Always use latest": "Завжди використовувати останню версію",
+  "Send changes only": "Відправити тільки зміни",
+  "Receive changes only": "Отримати тільки зміни",
+  "Disabled": "Вимкнено",
+  "Checksum Method": "Метод контрольної суми",
+  "File Content (recommended)": "Вміст файлу (рекомендується)",
+  "File Name": "Ім'я файлу",
+  "Device Name": "Ім'я пристрою",
+  "Sync Tolerance": "Допустима похибка синхронізації",
+  "Precision: {{precision}} decimal places": "Точність: {{precision}} десяткових знаків",
+  "Connect to your KOReader Sync server.": "Підключіться до свого сервера синхронізації KOReader.",
+  "Server URL": "URL сервера",
+  "Username": "Ім'я користувача",
+  "Your Username": "Ваше ім'я користувача",
+  "Password": "Пароль",
+  "Connect": "Підключитися",
+  "KOReader Sync": "Синхронізація KOReader",
+  "Sync Conflict": "Конфлікт синхронізації",
+  "Sync reading progress from \"{{deviceName}}\"?": "Синхронізувати прогрес читання з \"{{deviceName}}\"?",
+  "another device": "інший пристрій",
+  "Local Progress": "Локальний прогрес",
+  "Remote Progress": "Віддалений прогрес",
+  "Page {{page}} of {{total}} ({{percentage}}%)": "Сторінка {{page}} з {{total}} ({{percentage}}%)",
+  "Current position": "Поточна позиція",
+  "Approximately page {{page}} of {{total}} ({{percentage}}%)": "Приблизно сторінка {{page}} з {{total}} ({{percentage}}%)",
+  "Approximately {{percentage}}%": "Приблизно {{percentage}}%"
 }
diff --git a/apps/readest-app/public/locales/vi/translation.json b/apps/readest-app/public/locales/vi/translation.json
index f4f8a700..a6e69531 100644
--- a/apps/readest-app/public/locales/vi/translation.json
+++ b/apps/readest-app/public/locales/vi/translation.json
@@ -467,5 +467,38 @@
   "Are you sure to delete the local copy of the selected book?": "Bạn có chắc chắn muốn xóa bản sao cục bộ của cuốn sách đã chọn không?",
   "Remove from Cloud & Device": "Xóa khỏi Đám mây & Thiết bị",
   "Remove from Cloud Only": "Xóa chỉ khỏi Đám mây",
-  "Remove from Device Only": "Xóa chỉ khỏi Thiết bị"
+  "Remove from Device Only": "Xóa chỉ khỏi Thiết bị",
+  "Error": "Lỗi",
+  "Disconnected": "Mất kết nối",
+  "KOReader Sync Settings": "Cài đặt đồng bộ KOReader",
+  "Connected as {{username}}": "Đã kết nối với {{username}}",
+  "Disconnect": "Ngắt kết nối",
+  "Sync Strategy": "Chiến lược đồng bộ",
+  "Ask on conflict": "Hỏi khi có xung đột",
+  "Always use latest": "Luôn sử dụng phiên bản mới nhất",
+  "Send changes only": "Chỉ gửi thay đổi",
+  "Receive changes only": "Chỉ nhận thay đổi",
+  "Disabled": "Đã tắt",
+  "Checksum Method": "Phương pháp kiểm tra",
+  "File Content (recommended)": "Nội dung tệp (được khuyến nghị)",
+  "File Name": "Tên tệp",
+  "Device Name": "Tên thiết bị",
+  "Sync Tolerance": "Độ dung sai đồng bộ",
+  "Precision: {{precision}} decimal places": "Độ chính xác: {{precision}} chữ số thập phân",
+  "Connect to your KOReader Sync server.": "Kết nối với máy chủ đồng bộ KOReader của bạn.",
+  "Server URL": "URL máy chủ",
+  "Username": "Tên người dùng",
+  "Your Username": "Tên người dùng của bạn",
+  "Password": "Mật khẩu",
+  "Connect": "Kết nối",
+  "KOReader Sync": "Đồng bộ KOReader",
+  "Sync Conflict": "Xung đột đồng bộ",
+  "Sync reading progress from \"{{deviceName}}\"?": "Đồng bộ tiến độ đọc từ \"{{deviceName}}\"?",
+  "another device": "thiết bị khác",
+  "Local Progress": "Tiến độ cục bộ",
+  "Remote Progress": "Tiến độ từ xa",
+  "Page {{page}} of {{total}} ({{percentage}}%)": "Trang {{page}} của {{total}} ({{percentage}}%)",
+  "Current position": "Vị trí hiện tại",
+  "Approximately page {{page}} of {{total}} ({{percentage}}%)": "Khoảng trang {{page}} của {{total}} ({{percentage}}%)",
+  "Approximately {{percentage}}%": "Khoảng {{percentage}}%"
 }
diff --git a/apps/readest-app/public/locales/zh-CN/translation.json b/apps/readest-app/public/locales/zh-CN/translation.json
index 7832d4ac..758c5998 100644
--- a/apps/readest-app/public/locales/zh-CN/translation.json
+++ b/apps/readest-app/public/locales/zh-CN/translation.json
@@ -467,5 +467,38 @@
   "Are you sure to delete the local copy of the selected book?": "您确定要删除所选书籍的本地副本吗？",
   "Remove from Cloud & Device": "从云端和设备中移除",
   "Remove from Cloud Only": "仅从云端移除",
-  "Remove from Device Only": "仅从设备中移除"
+  "Remove from Device Only": "仅从设备中移除",
+  "Error": "错误",
+  "Disconnected": "已断开连接",
+  "KOReader Sync Settings": "KOReader 同步设置",
+  "Connected as {{username}}": "已连接为 {{username}}",
+  "Disconnect": "断开连接",
+  "Sync Strategy": "同步策略",
+  "Ask on conflict": "发生冲突时询问",
+  "Always use latest": "始终使用最新",
+  "Send changes only": "仅发送更改",
+  "Receive changes only": "仅接收更改",
+  "Disabled": "已禁用",
+  "Checksum Method": "校验和方法",
+  "File Content (recommended)": "文件内容（推荐）",
+  "File Name": "文件名",
+  "Device Name": "设备名称",
+  "Sync Tolerance": "同步容忍度",
+  "Precision: {{precision}} decimal places": "精度：{{precision}} 位小数",
+  "Connect to your KOReader Sync server.": "连接到您的 KOReader 同步服务器。",
+  "Server URL": "服务器 URL",
+  "Username": "用户名",
+  "Your Username": "您的用户名",
+  "Password": "密码",
+  "Connect": "连接",
+  "KOReader Sync": "KOReader 同步",
+  "Sync Conflict": "同步冲突",
+  "Sync reading progress from \"{{deviceName}}\"?": "从 \"{{deviceName}}\" 同步阅读进度？",
+  "another device": "另一台设备",
+  "Local Progress": "本地进度",
+  "Remote Progress": "远程进度",
+  "Page {{page}} of {{total}} ({{percentage}}%)": "第 {{page}} 页，共 {{total}} 页 ({{percentage}}%)",
+  "Current position": "当前位置",
+  "Approximately page {{page}} of {{total}} ({{percentage}}%)": "大约第 {{page}} 页，共 {{total}} 页 ({{percentage}}%)",
+  "Approximately {{percentage}}%": "大约 {{percentage}}%"
 }
diff --git a/apps/readest-app/public/locales/zh-TW/translation.json b/apps/readest-app/public/locales/zh-TW/translation.json
index dd7cd022..052d3312 100644
--- a/apps/readest-app/public/locales/zh-TW/translation.json
+++ b/apps/readest-app/public/locales/zh-TW/translation.json
@@ -467,5 +467,38 @@
   "Are you sure to delete the local copy of the selected book?": "您確定要刪除所選書籍的本地副本嗎？",
   "Remove from Cloud & Device": "從雲端和設備中移除",
   "Remove from Cloud Only": "僅從雲端移除",
-  "Remove from Device Only": "僅從設備中移除"
+  "Remove from Device Only": "僅從設備中移除",
+  "Error": "錯誤",
+  "Disconnected": "已斷開連接",
+  "KOReader Sync Settings": "KOReader 同步設置",
+  "Connected as {{username}}": "已連接為 {{username}}",
+  "Disconnect": "斷開連接",
+  "Sync Strategy": "同步策略",
+  "Ask on conflict": "發生衝突時詢問",
+  "Always use latest": "始終使用最新",
+  "Send changes only": "僅發送更改",
+  "Receive changes only": "僅接收更改",
+  "Disabled": "已禁用",
+  "Checksum Method": "校驗和方法",
+  "File Content (recommended)": "文件內容（推薦）",
+  "File Name": "文件名",
+  "Device Name": "設備名稱",
+  "Sync Tolerance": "同步容忍度",
+  "Precision: {{precision}} decimal places": "精度：{{precision}} 位小數",
+  "Connect to your KOReader Sync server.": "連接到您的 KOReader 同步伺服器。",
+  "Server URL": "伺服器 URL",
+  "Username": "用戶名",
+  "Your Username": "您的用戶名",
+  "Password": "密碼",
+  "Connect": "連接",
+  "KOReader Sync": "KOReader 同步",
+  "Sync Conflict": "同步衝突",
+  "Sync reading progress from \"{{deviceName}}\"?": "從 \"{{deviceName}}\" 同步閱讀進度？",
+  "another device": "另一個設備",
+  "Local Progress": "本地進度",
+  "Remote Progress": "遠程進度",
+  "Page {{page}} of {{total}} ({{percentage}}%)": "第 {{page}} 頁，共 {{total}} 頁 ({{percentage}}%)",
+  "Current position": "當前位置",
+  "Approximately page {{page}} of {{total}} ({{percentage}}%)": "大約第 {{page}} 頁，共 {{total}} 頁 ({{percentage}}%)",
+  "Approximately {{percentage}}%": "大約 {{percentage}}%"
 }
diff --git a/apps/readest-app/src/app/library/components/KOSyncSettings.tsx b/apps/readest-app/src/app/library/components/KOSyncSettings.tsx
new file mode 100644
index 00000000..9f738b21
--- /dev/null
+++ b/apps/readest-app/src/app/library/components/KOSyncSettings.tsx
@@ -0,0 +1,368 @@
+import React, { useState, useEffect, useMemo, useCallback } from 'react';
+import { md5 } from 'js-md5';
+import clsx from 'clsx';
+import { type as osType } from '@tauri-apps/plugin-os';
+import Dialog from '@/components/Dialog';
+import { useTranslation } from '@/hooks/useTranslation';
+import { useSettingsStore } from '@/store/settingsStore';
+import { useEnv } from '@/context/EnvContext';
+import { eventDispatcher } from '@/utils/event';
+import { KOSyncClient } from '@/services/sync/KOSyncClient';
+import { KoreaderSyncChecksumMethod, KoreaderSyncStrategy } from '@/types/settings';
+import { v4 as uuidv4 } from 'uuid';
+import { debounce } from '@/utils/debounce';
+import { getOSPlatform } from '@/utils/misc';
+
+type Option = {
+  value: string;
+  label: string;
+};
+
+type SelectProps = {
+  value: string;
+  onChange: (e: React.ChangeEvent<HTMLSelectElement>) => void;
+  options: Option[];
+  disabled?: boolean;
+  className?: string;
+};
+
+const StyledSelect: React.FC<SelectProps> = ({
+  value,
+  onChange,
+  options,
+  className,
+  disabled = false,
+}) => {
+  return (
+    <select
+      value={value}
+      onChange={onChange}
+      className={clsx(
+        'select select-bordered h-12 w-full text-sm focus:outline-none focus:ring-0',
+        className,
+      )}
+      disabled={disabled}
+    >
+      {options.map(({ value, label }) => (
+        <option key={value} value={value}>
+          {label}
+        </option>
+      ))}
+    </select>
+  );
+};
+
+export const setKOSyncSettingsWindowVisible = (visible: boolean) => {
+  const dialog = document.getElementById('kosync_settings_window');
+  if (dialog) {
+    const event = new CustomEvent('setKOSyncSettingsVisibility', {
+      detail: { visible },
+    });
+    dialog.dispatchEvent(event);
+  }
+};
+
+export const KOSyncSettingsWindow: React.FC = () => {
+  const _ = useTranslation();
+  const { settings, setSettings, saveSettings } = useSettingsStore();
+  const { envConfig, appService } = useEnv();
+
+  const [isOpen, setIsOpen] = useState(false);
+  const [url, setUrl] = useState(settings.koreaderSyncServerUrl || '');
+  const [username, setUsername] = useState(settings.koreaderSyncUsername || '');
+  const [password, setPassword] = useState('');
+  const [isConnecting, setIsConnecting] = useState(false);
+  const [connectionStatus, setConnectionStatus] = useState('');
+  const [deviceName, setDeviceName] = useState('');
+  const [osName, setOsName] = useState('');
+
+  const [toleranceSliderValue, setToleranceSliderValue] = useState(() => {
+    const tolerance = settings.koreaderSyncPercentageTolerance;
+    return tolerance && tolerance > 0 ? Math.round(-Math.log10(tolerance)) : 4;
+  });
+
+  // Get the OS name once
+  useEffect(() => {
+    const getOsName = async () => {
+      let name = '';
+      if (appService?.appPlatform === 'tauri') {
+        name = await osType();
+      } else {
+        const platform = getOSPlatform();
+        if (platform !== 'unknown') {
+          name = platform;
+        }
+      }
+      setOsName(name ? name.charAt(0).toUpperCase() + name.slice(1) : '');
+    };
+    getOsName();
+  }, [appService]);
+
+  useEffect(() => {
+    const defaultName = osName ? `Readest (${osName})` : 'Readest';
+    setDeviceName(settings.koreaderSyncDeviceName || defaultName);
+  }, [settings.koreaderSyncDeviceName, osName]);
+
+  const isConfigured = useMemo(
+    () => !!settings.koreaderSyncUserkey,
+    [settings.koreaderSyncUserkey],
+  );
+
+  const debouncedSaveDeviceName = useCallback(
+    debounce((newDeviceName: string) => {
+      const newSettings = { ...settings, koreaderSyncDeviceName: newDeviceName };
+      setSettings(newSettings);
+      saveSettings(envConfig, newSettings);
+    }, 500),
+    [settings, setSettings, saveSettings, envConfig],
+  );
+
+  const handleDeviceNameChange = (e: React.ChangeEvent<HTMLInputElement>) => {
+    const newName = e.target.value;
+    setDeviceName(newName);
+    debouncedSaveDeviceName(newName);
+  };
+
+  useEffect(() => {
+    const handleCustomEvent = (event: CustomEvent) => {
+      setIsOpen(event.detail.visible);
+      if (event.detail.visible) {
+        setUrl(settings.koreaderSyncServerUrl || '');
+        setUsername(settings.koreaderSyncUsername || '');
+        setPassword('');
+        setConnectionStatus('');
+        // Sync the slider with the current settings when opening
+        const tolerance = settings.koreaderSyncPercentageTolerance;
+        setToleranceSliderValue(
+          tolerance && tolerance > 0 ? Math.round(-Math.log10(tolerance)) : 4,
+        );
+      }
+    };
+    const el = document.getElementById('kosync_settings_window');
+    el?.addEventListener('setKOSyncSettingsVisibility', handleCustomEvent as EventListener);
+    return () => {
+      el?.removeEventListener('setKOSyncSettingsVisibility', handleCustomEvent as EventListener);
+    };
+  }, [
+    settings.koreaderSyncServerUrl,
+    settings.koreaderSyncUsername,
+    settings.koreaderSyncPercentageTolerance,
+  ]);
+
+  const handleConnect = async () => {
+    setIsConnecting(true);
+
+    let deviceId = settings.koreaderSyncDeviceId;
+    if (!deviceId) {
+      deviceId = uuidv4().replace(/-/g, '').toUpperCase();
+    }
+
+    const client = new KOSyncClient(
+      url,
+      username,
+      md5(password),
+      settings.koreaderSyncChecksumMethod,
+      deviceId,
+      deviceName,
+    );
+    const result = await client.connect(username, password);
+
+    if (result.success) {
+      const newSettings = {
+        ...settings,
+        koreaderSyncServerUrl: url,
+        koreaderSyncUsername: username,
+        koreaderSyncUserkey: md5(password),
+        koreaderSyncDeviceId: deviceId,
+        koreaderSyncDeviceName: deviceName,
+        koreaderSyncStrategy:
+          settings.koreaderSyncStrategy === 'disabled' ? 'prompt' : settings.koreaderSyncStrategy,
+      };
+      setSettings(newSettings);
+      await saveSettings(envConfig, newSettings);
+      eventDispatcher.dispatch('toast', {
+        message: _(result.message || 'Successfully connected!'),
+        type: 'success',
+      });
+    } else {
+      setConnectionStatus('');
+      eventDispatcher.dispatch('toast', {
+        message: `${_('Error')}: ${_(result.message || 'Connection error')}`,
+        type: 'error',
+      });
+    }
+    setIsConnecting(false);
+    setPassword('');
+  };
+
+  const handleDisconnect = async () => {
+    const newSettings = {
+      ...settings,
+      koreaderSyncStrategy: 'disabled' as KoreaderSyncStrategy,
+      koreaderSyncUserkey: '',
+    };
+    setSettings(newSettings);
+    await saveSettings(envConfig, newSettings);
+    setUsername('');
+    eventDispatcher.dispatch('toast', { message: _('Disconnected'), type: 'info' });
+  };
+
+  const handleStrategyChange = async (e: React.ChangeEvent<HTMLSelectElement>) => {
+    const newStrategy = e.target.value as KoreaderSyncStrategy;
+    const newSettings = { ...settings, koreaderSyncStrategy: newStrategy };
+    setSettings(newSettings);
+    await saveSettings(envConfig, newSettings);
+  };
+
+  const handleChecksumMethodChange = async (e: React.ChangeEvent<HTMLSelectElement>) => {
+    const newMethod = e.target.value as KoreaderSyncChecksumMethod;
+    const newSettings = { ...settings, koreaderSyncChecksumMethod: newMethod };
+    setSettings(newSettings);
+    await saveSettings(envConfig, newSettings);
+  };
+
+  const handleToleranceChange = async (e: React.ChangeEvent<HTMLInputElement>) => {
+    const sliderValue = parseInt(e.target.value, 10);
+    setToleranceSliderValue(sliderValue);
+    // Calculate the actual tolerance from the slider value (e.g., 4 -> 0.0001)
+    const newTolerance = Math.pow(10, -sliderValue);
+
+    const newSettings = { ...settings, koreaderSyncPercentageTolerance: newTolerance };
+    setSettings(newSettings);
+    await saveSettings(envConfig, newSettings);
+  };
+
+  return (
+    <Dialog
+      id='kosync_settings_window'
+      isOpen={isOpen}
+      onClose={() => setIsOpen(false)}
+      title={_('KOReader Sync Settings')}
+      boxClassName='sm:!min-w-[520px] sm:h-auto'
+    >
+      <div className='flex flex-col gap-4 p-2 sm:p-4'>
+        {isConfigured ? (
+          <>
+            <div className='text-center'>
+              <p className='text-base-content/80 py-2 text-sm'>
+                {_('Connected as {{username}}', { username: settings.koreaderSyncUsername })}
+              </p>
+              <button className='btn btn-warning h-12 min-h-12 w-full' onClick={handleDisconnect}>
+                {_('Disconnect')}
+              </button>
+            </div>
+            <div className='form-control w-full'>
+              <label className='label py-1'>
+                <span className='label-text font-medium'>{_('Sync Strategy')}</span>
+              </label>
+              <StyledSelect
+                value={settings.koreaderSyncStrategy}
+                onChange={handleStrategyChange}
+                options={[
+                  { value: 'prompt', label: _('Ask on conflict') },
+                  { value: 'silent', label: _('Always use latest') },
+                  { value: 'send', label: _('Send changes only') },
+                  { value: 'receive', label: _('Receive changes only') },
+                  { value: 'disable', label: _('Disabled') },
+                ]}
+              />
+            </div>
+            <div className='form-control w-full'>
+              <label className='label py-1'>
+                <span className='label-text font-medium'>{_('Checksum Method')}</span>
+              </label>
+              <StyledSelect
+                value={settings.koreaderSyncChecksumMethod}
+                onChange={handleChecksumMethodChange}
+                options={[
+                  { value: 'binary', label: _('File Content (recommended)') },
+                  { value: 'filename', label: _('File Name') },
+                ]}
+              />
+            </div>
+            <div className='form-control w-full'>
+              <label className='label py-1'>
+                <span className='label-text font-medium'>{_('Device Name')}</span>
+              </label>
+              <input
+                type='text'
+                placeholder={osName ? `Readest (${osName})` : 'Readest'}
+                className='input input-bordered h-12 w-full focus:outline-none focus:ring-0'
+                value={deviceName}
+                onChange={handleDeviceNameChange}
+              />
+            </div>
+            <div className='form-control w-full'>
+              <label className='label py-1'>
+                <span className='label-text font-medium'>{_('Sync Tolerance')}</span>
+              </label>
+              <input
+                type='range'
+                min='0'
+                max='15'
+                value={toleranceSliderValue}
+                onChange={handleToleranceChange}
+                className='range range-primary'
+              />
+              <div className='text-base-content/70 mt-2 text-center text-xs'>
+                {_('Precision: {{precision}} decimal places', { precision: toleranceSliderValue })}
+              </div>
+            </div>
+          </>
+        ) : (
+          <>
+            <p className='text-base-content/70 pt-2 text-center text-sm'>
+              {_('Connect to your KOReader Sync server.')}
+            </p>
+            <div className='form-control w-full'>
+              <label className='label py-1'>
+                <span className='label-text font-medium'>{_('Server URL')}</span>
+              </label>
+              <input
+                type='text'
+                placeholder='https://koreader.sync.server'
+                className='input input-bordered h-12 w-full'
+                value={url}
+                onChange={(e) => setUrl(e.target.value)}
+              />
+            </div>
+            <div className='form-control w-full'>
+              <label className='label py-1'>
+                <span className='label-text font-medium'>{_('Username')}</span>
+              </label>
+              <input
+                type='text'
+                placeholder={_('Your Username')}
+                className='input input-bordered h-12 w-full'
+                value={username}
+                onChange={(e) => setUsername(e.target.value)}
+              />
+            </div>
+            <div className='form-control w-full'>
+              <label className='label py-1'>
+                <span className='label-text font-medium'>{_('Password')}</span>
+              </label>
+              <input
+                type='password'
+                placeholder={_('Your Password')}
+                className='input input-bordered h-12 w-full'
+                value={password}
+                onChange={(e) => setPassword(e.target.value)}
+              />
+            </div>
+            <button
+              className='btn btn-primary mt-2 h-12 min-h-12 w-full'
+              onClick={handleConnect}
+              disabled={isConnecting || !url || !username || !password}
+            >
+              {isConnecting ? <span className='loading loading-spinner'></span> : _('Connect')}
+            </button>
+            {connectionStatus && (
+              <div className='text-error h-4 text-center text-sm'>{connectionStatus}</div>
+            )}
+          </>
+        )}
+      </div>
+    </Dialog>
+  );
+};
diff --git a/apps/readest-app/src/app/library/components/SettingsMenu.tsx b/apps/readest-app/src/app/library/components/SettingsMenu.tsx
index cf258794..dbae7fc5 100644
--- a/apps/readest-app/src/app/library/components/SettingsMenu.tsx
+++ b/apps/readest-app/src/app/library/components/SettingsMenu.tsx
@@ -8,6 +8,7 @@ import { TbSunMoon } from 'react-icons/tb';
 import { BiMoon, BiSun } from 'react-icons/bi';
 
 import { setAboutDialogVisible } from '@/components/AboutWindow';
+import { setKOSyncSettingsWindowVisible } from './KOSyncSettings';
 import { isTauriAppPlatform, isWebAppPlatform } from '@/services/environment';
 import { DOWNLOAD_READEST_URL } from '@/services/constants';
 import { useAuth } from '@/context/AuthContext';
@@ -158,6 +159,11 @@ const SettingsMenu: React.FC<SettingsMenuProps> = ({ setIsDropdownOpen }) => {
     setIsTelemetryEnabled(settings.telemetryEnabled);
   };
 
+  const showKoSyncSettingsWindow = () => {
+    setKOSyncSettingsWindowVisible(true);
+    setIsDropdownOpen?.(false);
+  };
+
   const handleUpgrade = () => {
     navigateToProfile(router);
     setIsDropdownOpen?.(false);
@@ -268,6 +274,8 @@ const SettingsMenu: React.FC<SettingsMenuProps> = ({ setIsDropdownOpen }) => {
         onClick={cycleThemeMode}
       />
       <hr className='border-base-200 my-1' />
+      <MenuItem label={_('KOReader Sync')} onClick={showKoSyncSettingsWindow} />
+      <hr className='border-base-200 my-1' />
       {user && userPlan === 'free' && !appService?.isIOSApp && (
         <MenuItem label={_('Upgrade to Readest Premium')} onClick={handleUpgrade} />
       )}
diff --git a/apps/readest-app/src/app/library/page.tsx b/apps/readest-app/src/app/library/page.tsx
index 7d560a11..13cffb3b 100644
--- a/apps/readest-app/src/app/library/page.tsx
+++ b/apps/readest-app/src/app/library/page.tsx
@@ -48,6 +48,7 @@ import {
 } from '@/utils/window';
 
 import { AboutWindow } from '@/components/AboutWindow';
+import { KOSyncSettingsWindow } from './components/KOSyncSettings';
 import { UpdaterWindow } from '@/components/UpdaterWindow';
 import { BookMetadata } from '@/libs/document';
 import { BookDetailModal } from '@/components/metadata';
@@ -753,6 +754,7 @@ const LibraryPageContent = ({ searchParams }: { searchParams: ReadonlyURLSearchP
         />
       )}
       <AboutWindow />
+      <KOSyncSettingsWindow />
       <UpdaterWindow />
       <Toast />
     </div>
diff --git a/apps/readest-app/src/app/reader/components/ConfirmSyncDialog.tsx b/apps/readest-app/src/app/reader/components/ConfirmSyncDialog.tsx
new file mode 100644
index 00000000..0f8e25e3
--- /dev/null
+++ b/apps/readest-app/src/app/reader/components/ConfirmSyncDialog.tsx
@@ -0,0 +1,49 @@
+import React from 'react';
+import Dialog from '@/components/Dialog';
+import { useTranslation } from '@/hooks/useTranslation';
+import { SyncDetails } from '../hooks/useKOSync';
+
+interface ConfirmSyncDialogProps {
+  details: SyncDetails | null;
+  onConfirmLocal: () => void;
+  onConfirmRemote: () => void;
+  onClose: () => void;
+}
+
+const ConfirmSyncDialog: React.FC<ConfirmSyncDialogProps> = ({
+  details,
+  onConfirmLocal,
+  onConfirmRemote,
+  onClose,
+}) => {
+  const _ = useTranslation();
+
+  if (!details) return null;
+
+  return (
+    <Dialog isOpen={true} onClose={onClose} title={_('Sync Conflict')}>
+      <p className='py-4 text-center'>
+        {_('Sync reading progress from "{{deviceName}}"?', {
+          deviceName: details.remote.device || _('another device'),
+        })}
+      </p>
+      <div className='mt-4 space-y-4'>
+        <button className='btn h-auto w-full flex-col items-start py-2' onClick={onConfirmLocal}>
+          <span>{_('Local Progress')}</span>
+          <span className='text-xs font-normal normal-case text-gray-500'>
+            {details.local.preview}
+          </span>
+        </button>
+        <button
+          className='btn btn-primary h-auto w-full flex-col items-start py-2'
+          onClick={onConfirmRemote}
+        >
+          <span>{_('Remote Progress')}</span>
+          <span className='text-xs font-normal normal-case'>{details.remote.preview}</span>
+        </button>
+      </div>
+    </Dialog>
+  );
+};
+
+export default ConfirmSyncDialog;
diff --git a/apps/readest-app/src/app/reader/components/FoliateViewer.tsx b/apps/readest-app/src/app/reader/components/FoliateViewer.tsx
index d71dec94..c5cbb82e 100644
--- a/apps/readest-app/src/app/reader/components/FoliateViewer.tsx
+++ b/apps/readest-app/src/app/reader/components/FoliateViewer.tsx
@@ -13,6 +13,7 @@ import { usePagination } from '../hooks/usePagination';
 import { useFoliateEvents } from '../hooks/useFoliateEvents';
 import { useProgressSync } from '../hooks/useProgressSync';
 import { useProgressAutoSave } from '../hooks/useProgressAutoSave';
+import { useKOSync } from '../hooks/useKOSync';
 import {
   applyFixedlayoutStyles,
   applyImageStyle,
@@ -42,6 +43,7 @@ import { lockScreenOrientation } from '@/utils/bridge';
 import { useTextTranslation } from '../hooks/useTextTranslation';
 import { manageSyntaxHighlighting } from '@/utils/highlightjs';
 import { getViewInsets } from '@/utils/insets';
+import ConfirmSyncDialog from './ConfirmSyncDialog';
 
 declare global {
   interface Window {
@@ -77,6 +79,12 @@ const FoliateViewer: React.FC<{
   useUICSS(bookKey);
   useProgressSync(bookKey);
   useProgressAutoSave(bookKey);
+  const {
+    syncState,
+    conflictDetails,
+    resolveConflictWithLocal,
+    resolveConflictWithRemote,
+  } = useKOSync(bookKey);
   useTextTranslation(bookKey, viewRef.current);
 
   const progressRelocateHandler = (event: Event) => {
@@ -349,12 +357,22 @@ const FoliateViewer: React.FC<{
   ]);
 
   return (
-    <div
-      ref={containerRef}
-      className='foliate-viewer h-[100%] w-[100%]'
-      {...mouseHandlers}
-      {...touchHandlers}
-    />
+    <>
+      <div
+        ref={containerRef}
+        className='foliate-viewer h-[100%] w-[100%]'
+        {...mouseHandlers}
+        {...touchHandlers}
+      />
+      {syncState === 'conflict' && conflictDetails && (
+        <ConfirmSyncDialog
+          details={conflictDetails}
+          onConfirmLocal={resolveConflictWithLocal}
+          onConfirmRemote={resolveConflictWithRemote}
+          onClose={resolveConflictWithLocal}
+        />
+      )}
+    </>
   );
 };
 
diff --git a/apps/readest-app/src/app/reader/components/ReaderContent.tsx b/apps/readest-app/src/app/reader/components/ReaderContent.tsx
index 83254801..c66b9859 100644
--- a/apps/readest-app/src/app/reader/components/ReaderContent.tsx
+++ b/apps/readest-app/src/app/reader/components/ReaderContent.tsx
@@ -1,8 +1,7 @@
 'use client';
 
 import clsx from 'clsx';
-import * as React from 'react';
-import { useState, useRef, useEffect } from 'react';
+import React, { useEffect, useRef, useState } from 'react';
 import { useRouter, useSearchParams } from 'next/navigation';
 
 import { Book } from '@/types/book';
@@ -75,6 +74,10 @@ const ReaderContent: React.FC<{ ids?: string; settings: SystemSettings }> = ({ i
       return true;
     };
     eventDispatcher.onSync('show-book-details', handleShowBookDetails);
+
+    return () => {
+      eventDispatcher.offSync('show-book-details', handleShowBookDetails);
+    };
     // eslint-disable-next-line react-hooks/exhaustive-deps
   }, []);
 
@@ -106,8 +109,9 @@ const ReaderContent: React.FC<{ ids?: string; settings: SystemSettings }> = ({ i
     const { book } = getBookData(bookKey) || {};
     const { isPrimary } = getViewState(bookKey) || {};
     if (isPrimary && book && config) {
-      eventDispatcher.dispatch('sync-book-progress', { bookKey });
       const settings = useSettingsStore.getState().settings;
+      eventDispatcher.dispatch('sync-book-progress', { bookKey });
+      eventDispatcher.dispatch('flush-koreader-sync', { bookKey });
       await saveConfig(envConfig, bookKey, config, settings);
     }
   };
diff --git a/apps/readest-app/src/app/reader/hooks/useKOSync.ts b/apps/readest-app/src/app/reader/hooks/useKOSync.ts
new file mode 100644
index 00000000..acace5a7
--- /dev/null
+++ b/apps/readest-app/src/app/reader/hooks/useKOSync.ts
@@ -0,0 +1,482 @@
+import { useState, useEffect, useCallback, useRef, useMemo } from 'react';
+import { md5 } from 'js-md5';
+import { type as osType } from '@tauri-apps/plugin-os';
+import { useEnv } from '@/context/EnvContext';
+import { useSettingsStore } from '@/store/settingsStore';
+import { useReaderStore } from '@/store/readerStore';
+import { useBookDataStore } from '@/store/bookDataStore';
+import { useTranslation } from '@/hooks/useTranslation';
+import { KOSyncClient, KoSyncProgress } from '@/services/sync/KOSyncClient';
+import { Book, BookFormat } from '@/types/book';
+import { BookDoc } from '@/libs/document';
+import { debounce } from '@/utils/debounce';
+import { eventDispatcher } from '@/utils/event';
+import { getCFIFromXPointer, XCFI } from '@/utils/xcfi';
+
+const PAGINATED_FORMATS: Set<BookFormat> = new Set(['PDF', 'CBZ']);
+
+type SyncState = 'idle' | 'checking' | 'conflict' | 'synced' | 'error';
+
+export interface SyncDetails {
+  book: Book;
+  bookDoc: BookDoc;
+  local: {
+    cfi?: string;
+    preview: string;
+  };
+  remote: KoSyncProgress & {
+    preview: string;
+    percentage?: number;
+  };
+}
+
+export const useKOSync = (bookKey: string) => {
+  const _ = useTranslation();
+  const { settings } = useSettingsStore();
+  const { getProgress, getView } = useReaderStore();
+  const { getBookData } = useBookDataStore();
+  const { appService } = useEnv();
+  const progress = getProgress(bookKey);
+
+  const [syncState, setSyncState] = useState<SyncState>('idle');
+  const [conflictDetails, setConflictDetails] = useState<SyncDetails | null>(null);
+  const [errorMessage] = useState<string | null>(null);
+
+  const syncCompletedForKey = useRef<string | null>(null);
+  const lastPushedCfiRef = useRef<string | null>(null);
+  const bookData = getBookData(bookKey);
+  const book = bookData?.book;
+  const bookDoc = bookData?.bookDoc;
+
+  useEffect(() => {
+    lastPushedCfiRef.current = null;
+    syncCompletedForKey.current = null;
+    setSyncState('idle');
+  }, [bookKey]);
+
+  const mapProgressToServerFormat = useCallback(() => {
+    const currentProgress = getProgress(bookKey);
+    const currentBook = getBookData(bookKey)?.book;
+    if (!currentProgress || !currentBook) return null;
+
+    let progressStr: string;
+    let percentage: number;
+
+    if (PAGINATED_FORMATS.has(currentBook.format)) {
+      const page = (currentProgress.section?.current ?? 0) + 1;
+      const totalPages = currentProgress.section?.total ?? 0;
+      progressStr = page.toString();
+      percentage = totalPages > 0 ? page / totalPages : 0;
+    } else {
+      progressStr = currentProgress.location;
+      const view = getView(bookKey);
+
+      if (view && progressStr) {
+        try {
+          const content = view.renderer.getContents()[0];
+          if (content) {
+            const { doc, index: spineIndex } = content;
+            const converter = new XCFI(doc, spineIndex || 0);
+            const xpointerResult = converter.cfiToXPointer(progressStr);
+
+            progressStr = xpointerResult.xpointer;
+          }
+        } catch (error) {
+          console.error(
+            'Failed to convert CFI to XPointer. Progress will be sent as percentage only.',
+            error,
+          );
+        }
+      }
+
+      const page = currentProgress.pageinfo?.current ?? 0;
+      const totalPages = currentProgress.pageinfo?.total ?? 0;
+      percentage = totalPages > 0 ? (page + 1) / totalPages : 0;
+    }
+
+    return { progressStr, percentage };
+  }, [bookKey, getProgress, getBookData, getView]);
+
+  const pushProgress = useMemo(
+    () =>
+      debounce(async () => {
+        const { settings: currentSettings } = useSettingsStore.getState();
+        const currentBook = getBookData(bookKey)?.book;
+
+        const { koreaderSyncUsername, koreaderSyncUserkey, koreaderSyncStrategy } = currentSettings;
+        if (
+          !koreaderSyncUsername ||
+          !koreaderSyncUserkey ||
+          ['receive', 'disable'].includes(koreaderSyncStrategy) ||
+          !currentBook
+        )
+          return;
+
+        const getDocumentDigest = (bookToDigest: Book): string => {
+          if (currentSettings.koreaderSyncChecksumMethod === 'filename') {
+            const filename = bookToDigest.sourceTitle || bookToDigest.title;
+            const normalizedPath = filename.replace(/\\/g, '/');
+            return md5(
+              normalizedPath.split('/').pop()?.split('.').slice(0, -1).join('.') || normalizedPath,
+            );
+          }
+          return bookToDigest.hash;
+        };
+
+        const getDeviceName = async () => {
+          if (currentSettings.koreaderSyncDeviceName) return currentSettings.koreaderSyncDeviceName;
+          if (appService?.appPlatform === 'tauri') {
+            const name = await osType();
+            return `Readest (${name.charAt(0).toUpperCase() + name.slice(1)})`;
+          }
+          return 'Readest';
+        };
+
+        const digest = getDocumentDigest(currentBook);
+        const progressData = mapProgressToServerFormat();
+        if (!digest || !progressData) return;
+
+        if (progressData.progressStr === lastPushedCfiRef.current) return;
+
+        const deviceName = await getDeviceName();
+        const client = new KOSyncClient(
+          currentSettings.koreaderSyncServerUrl,
+          currentSettings.koreaderSyncUsername,
+          currentSettings.koreaderSyncUserkey,
+          currentSettings.koreaderSyncChecksumMethod,
+          currentSettings.koreaderSyncDeviceId,
+          deviceName,
+        );
+
+        await client.updateProgress(currentBook, progressData.progressStr, progressData.percentage);
+        lastPushedCfiRef.current = progressData.progressStr;
+      }, 5000),
+    [bookKey, appService, getBookData, mapProgressToServerFormat],
+  );
+
+  useEffect(() => {
+    const handleFlush = (event: CustomEvent) => {
+      const { bookKey: syncBookKey } = event.detail;
+      if (syncBookKey === bookKey) {
+        pushProgress.flush();
+      }
+    };
+    eventDispatcher.on('flush-koreader-sync', handleFlush);
+    return () => {
+      eventDispatcher.off('flush-koreader-sync', handleFlush);
+      pushProgress.flush();
+    };
+  }, [bookKey, pushProgress]);
+
+  useEffect(() => {
+    const performInitialSync = async () => {
+      const { koreaderSyncUsername, koreaderSyncUserkey, koreaderSyncStrategy } = settings;
+      if (
+        !book ||
+        !bookDoc ||
+        !progress ||
+        !koreaderSyncUsername ||
+        !koreaderSyncUserkey ||
+        koreaderSyncStrategy === 'disabled'
+      )
+        return;
+
+      if (koreaderSyncStrategy === 'send') {
+        syncCompletedForKey.current = bookKey;
+        setSyncState('synced');
+        return;
+      }
+
+      setSyncState('checking');
+
+      const getDeviceName = async () => {
+        if (settings.koreaderSyncDeviceName) return settings.koreaderSyncDeviceName;
+        if (appService?.appPlatform === 'tauri') {
+          const name = await osType();
+          return `Readest (${name.charAt(0).toUpperCase() + name.slice(1)})`;
+        }
+        return 'Readest';
+      };
+
+      const deviceName = await getDeviceName();
+      const client = new KOSyncClient(
+        settings.koreaderSyncServerUrl,
+        settings.koreaderSyncUsername,
+        settings.koreaderSyncUserkey,
+        settings.koreaderSyncChecksumMethod,
+        settings.koreaderSyncDeviceId,
+        deviceName,
+      );
+      const remote = await client.getProgress(book);
+      lastPushedCfiRef.current = progress.location;
+
+      if (!remote?.progress || !remote?.timestamp) {
+        syncCompletedForKey.current = bookKey;
+        setSyncState('synced');
+        if (settings.koreaderSyncStrategy !== 'receive') {
+          pushProgress();
+          pushProgress.flush();
+        }
+        return;
+      }
+
+      const localTimestamp = bookData?.config?.updatedAt || book.updatedAt;
+      const remoteIsNewer = remote.timestamp * 1000 > localTimestamp;
+
+      const localIdentifier = PAGINATED_FORMATS.has(book.format)
+        ? progress.section?.current.toString()
+        : progress.location;
+      const isLocalCFI = localIdentifier?.startsWith('epubcfi');
+
+      const remoteIdentifier = PAGINATED_FORMATS.has(book.format)
+        ? (parseInt(remote.progress, 10) - 1).toString()
+        : remote.progress.startsWith('epubcfi')
+          ? remote.progress
+          : null;
+      const isRemoteCFI = remoteIdentifier?.startsWith('epubcfi');
+
+      let isProgressIdentical = false;
+      if (isLocalCFI && isRemoteCFI) {
+        isProgressIdentical = localIdentifier === remoteIdentifier;
+      }
+
+      if (!isProgressIdentical) {
+        const localPercentage = mapProgressToServerFormat()?.percentage ?? 0;
+        const remotePercentage = remote.percentage;
+
+        if (remotePercentage !== undefined && remotePercentage !== null) {
+          const tolerance = settings.koreaderSyncPercentageTolerance;
+          const percentageDifference = Math.abs(localPercentage - remotePercentage);
+          isProgressIdentical = percentageDifference < tolerance;
+        }
+      }
+
+      if (isProgressIdentical) {
+        lastPushedCfiRef.current = localIdentifier;
+        syncCompletedForKey.current = bookKey;
+        setSyncState('synced');
+        return;
+      }
+
+      if (
+        settings.koreaderSyncStrategy === 'receive' ||
+        (settings.koreaderSyncStrategy === 'silent' && remoteIsNewer)
+      ) {
+        const applyRemoteProgress = async () => {
+          const view = getView(bookKey);
+          if (view && remote.progress) {
+            if (PAGINATED_FORMATS.has(book.format)) {
+              const pageToGo = parseInt(remote.progress, 10);
+              if (!isNaN(pageToGo)) view.select(pageToGo - 1);
+            } else {
+              const isXPointer = remote.progress.startsWith('/body');
+              if (isXPointer) {
+                try {
+                  const content = view.renderer.getContents()[0];
+                  if (content) {
+                    const { doc, index } = content;
+                    const cfi = await getCFIFromXPointer(remote.progress, doc, index || 0, bookDoc);
+                    view.goTo(cfi);
+                    eventDispatcher.dispatch('toast', {
+                      message: _('Reading Progress Synced'),
+                      type: 'info',
+                    });
+                  }
+                } catch (error) {
+                  console.error(
+                    'Failed to convert XPointer to CFI, falling back to percentage.',
+                    error,
+                  );
+                  if (remote.percentage !== undefined && remote.percentage !== null) {
+                    view.goToFraction(remote.percentage);
+                  }
+                }
+              } else {
+                if (remote.percentage !== undefined && remote.percentage !== null) {
+                  view.goToFraction(remote.percentage);
+                }
+              }
+            }
+            eventDispatcher.dispatch('toast', {
+              message: _('Reading Progress Synced'),
+              type: 'info',
+            });
+          }
+        };
+
+        applyRemoteProgress();
+        syncCompletedForKey.current = bookKey;
+        setSyncState('synced');
+      } else if (settings.koreaderSyncStrategy === 'prompt') {
+        let localPreview = '';
+        let remotePreview = '';
+        const remotePercentage = remote.percentage || 0;
+
+        if (PAGINATED_FORMATS.has(book.format)) {
+          const localPageInfo = progress.section;
+          const localPercentage =
+            localPageInfo && localPageInfo.total > 0
+              ? Math.round(((localPageInfo.current + 1) / localPageInfo.total) * 100)
+              : 0;
+          localPreview = localPageInfo
+            ? _('Page {{page}} of {{total}} ({{percentage}}%)', {
+                page: localPageInfo.current + 1,
+                total: localPageInfo.total,
+                percentage: localPercentage,
+              })
+            : _('Current position');
+
+          const remotePage = parseInt(remote.progress, 10);
+          if (!isNaN(remotePage) && remotePercentage > 0) {
+            const localTotalPages = localPageInfo?.total ?? 0;
+            const remoteTotalPages = Math.round(remotePage / remotePercentage);
+            const pagesMatch = Math.abs(localTotalPages - remoteTotalPages) <= 1;
+
+            if (pagesMatch) {
+              remotePreview = _('Page {{page}} of {{total}} ({{percentage}}%)', {
+                page: remotePage,
+                total: remoteTotalPages,
+                percentage: Math.round(remotePercentage * 100),
+              });
+            } else {
+              remotePreview = _('Approximately page {{page}} of {{total}} ({{percentage}}%)', {
+                page: remotePage,
+                total: remoteTotalPages,
+                percentage: Math.round(remotePercentage * 100),
+              });
+            }
+          } else {
+            remotePreview = _('Approximately {{percentage}}%', {
+              percentage: Math.round(remotePercentage * 100),
+            });
+          }
+        } else {
+          const localPageInfo = progress.pageinfo;
+          const localPercentage =
+            localPageInfo && localPageInfo.total > 0
+              ? Math.round(((localPageInfo.current + 1) / localPageInfo.total) * 100)
+              : 0;
+          localPreview = `${progress.sectionLabel} (${localPercentage}%)`;
+
+          remotePreview = _('Approximately {{percentage}}%', {
+            percentage: Math.round(remotePercentage * 100),
+          });
+        }
+
+        setConflictDetails({
+          book,
+          bookDoc,
+          local: { cfi: progress.location, preview: localPreview },
+          remote: { ...remote, preview: remotePreview, percentage: remote.percentage },
+        });
+        setSyncState('conflict');
+      } else {
+        syncCompletedForKey.current = bookKey;
+        setSyncState('synced');
+      }
+    };
+
+    if (bookKey && book && progress && syncCompletedForKey.current !== bookKey) {
+      syncCompletedForKey.current = bookKey;
+      performInitialSync();
+    }
+  }, [
+    bookKey,
+    book,
+    bookDoc,
+    progress,
+    settings,
+    appService,
+    getBookData,
+    getProgress,
+    getView,
+    mapProgressToServerFormat,
+    pushProgress,
+    _,
+    bookData?.config?.updatedAt,
+  ]);
+
+  useEffect(() => {
+    if (syncState === 'synced' && progress) {
+      if (
+        settings.koreaderSyncStrategy !== 'receive' &&
+        settings.koreaderSyncStrategy !== 'disabled'
+      ) {
+        pushProgress();
+      }
+    }
+  }, [progress, syncState, settings.koreaderSyncStrategy, pushProgress]);
+
+  useEffect(() => {
+    return () => {
+      pushProgress.flush();
+    };
+  }, [pushProgress]);
+
+  const resolveConflictWithLocal = () => {
+    pushProgress();
+    pushProgress.flush();
+    setSyncState('synced');
+    setConflictDetails(null);
+  };
+
+  const resolveConflictWithRemote = async () => {
+    const view = getView(bookKey);
+    const remote = conflictDetails?.remote;
+    const currentBook = conflictDetails?.book;
+    const bookDoc = conflictDetails?.bookDoc;
+
+    if (view && remote?.progress && currentBook) {
+      if (PAGINATED_FORMATS.has(currentBook.format)) {
+        const localTotalPages = getProgress(bookKey)?.section?.total ?? 0;
+        const remotePage = parseInt(remote.progress, 10);
+        const remotePercentage = remote.percentage || 0;
+        const remoteTotalPages =
+          remotePercentage > 0 ? Math.round(remotePage / remotePercentage) : 0;
+
+        if (!isNaN(remotePage) && Math.abs(localTotalPages - remoteTotalPages) <= 1) {
+          console.log('Going to remote page:', remotePage);
+          view.select(remotePage - 1);
+        } else if (remote.percentage !== undefined && remote.percentage !== null) {
+          console.log('Going to remote percentage:', remote.percentage);
+          view.goToFraction(remote.percentage);
+        }
+      } else {
+        const isXPointer = remote.progress.startsWith('/body');
+        const isCFI = remote.progress.startsWith('epubcfi');
+
+        if (isXPointer) {
+          try {
+            const content = view.renderer.getContents()[0];
+            if (content) {
+              const { doc, index } = content;
+              const cfi = await getCFIFromXPointer(remote.progress, doc, index || 0, bookDoc);
+              view.goTo(cfi);
+            }
+          } catch (error) {
+            console.error('Failed to convert XPointer to CFI, falling back to percentage.', error);
+            if (remote.percentage !== undefined && remote.percentage !== null) {
+              view.goToFraction(remote.percentage);
+            }
+          }
+        } else if (isCFI) {
+          view.goTo(remote.progress);
+        } else if (remote.percentage !== undefined && remote.percentage !== null) {
+          view.goToFraction(remote.percentage);
+        }
+      }
+      eventDispatcher.dispatch('toast', { message: _('Reading Progress Synced'), type: 'info' });
+    }
+    setSyncState('synced');
+    setConflictDetails(null);
+  };
+
+  return {
+    syncState,
+    conflictDetails,
+    errorMessage,
+    resolveConflictWithLocal,
+    resolveConflictWithRemote,
+    pushProgress,
+  };
+};
diff --git a/apps/readest-app/src/libs/document.ts b/apps/readest-app/src/libs/document.ts
index d7198c67..2ec2a7b4 100644
--- a/apps/readest-app/src/libs/document.ts
+++ b/apps/readest-app/src/libs/document.ts
@@ -57,6 +57,8 @@ export interface SectionItem {
   size: number;
   linear: string;
   location?: Location;
+
+  createDocument: () => Promise<Document>;
 }
 
 export type BookMetadata = {
diff --git a/apps/readest-app/src/pages/api/kosync.ts b/apps/readest-app/src/pages/api/kosync.ts
new file mode 100644
index 00000000..1b78b61c
--- /dev/null
+++ b/apps/readest-app/src/pages/api/kosync.ts
@@ -0,0 +1,54 @@
+import type { NextApiRequest, NextApiResponse } from 'next';
+import { corsAllMethods, runMiddleware } from '@/utils/cors';
+import { KoSyncProxyPayload } from '@/types/kosync';
+
+export default async function handler(req: NextApiRequest, res: NextApiResponse) {
+  await runMiddleware(req, res, corsAllMethods);
+
+  const {
+    serverUrl,
+    endpoint,
+    method,
+    headers: clientHeaders,
+    body: clientBody,
+  } = req.body as KoSyncProxyPayload;
+
+  if (req.method !== 'POST') {
+    return res.status(405).json({ error: 'Method Not Allowed' });
+  }
+
+  if (!serverUrl || !endpoint) {
+    return res.status(400).json({ error: 'serverUrl and endpoint are required' });
+  }
+
+  const targetUrl = `${serverUrl.replace(/\/$/, '')}${endpoint}`;
+
+  try {
+    const response = await fetch(targetUrl, {
+      method: method,
+      headers: {
+        ...clientHeaders,
+        Accept: 'application/vnd.koreader.v1+json',
+        'Content-Type': 'application/json',
+      },
+      body: clientBody ? JSON.stringify(clientBody) : null,
+    });
+
+    const contentType = response.headers.get('content-type');
+    if (!contentType || !contentType.includes('application/json')) {
+      throw new Error('Invalid sync server response: Unexpected Content-Type.');
+    }
+
+    const data = await response.text();
+    res.status(response.status);
+    try {
+      res.json(JSON.parse(data));
+    } catch {
+      res.send(data);
+    }
+  } catch (error) {
+    console.error('[KOSYNC PROXY] Error:', error);
+    const errorMessage = error instanceof Error ? error.message : 'An unknown error occurred';
+    res.status(500).json({ error: 'Proxy request failed', details: errorMessage });
+  }
+}
diff --git a/apps/readest-app/src/services/appService.ts b/apps/readest-app/src/services/appService.ts
index c3dd79dd..5721c7da 100644
--- a/apps/readest-app/src/services/appService.ts
+++ b/apps/readest-app/src/services/appService.ts
@@ -1,6 +1,6 @@
-import { AppPlatform, AppService, OsPlatform } from '@/types/system';
-
+import { v4 as uuidv4 } from 'uuid';
 import { SystemSettings } from '@/types/settings';
+import { AppPlatform, AppService, OsPlatform } from '@/types/system';
 import { FileSystem, BaseDir, DeleteAction } from '@/types/system';
 import { Book, BookConfig, BookContent, BookFormat, ViewSettings } from '@/types/book';
 import {
@@ -116,11 +116,17 @@ export abstract class BaseAppService implements AppService {
         ...this.getDefaultViewSettings(),
         ...settings.globalViewSettings,
       };
+
+      if (!settings.koreaderSyncDeviceId) {
+        settings.koreaderSyncDeviceId = uuidv4();
+        await this.fs.writeFile(fp, base, JSON.stringify(settings));
+      }
     } catch {
       settings = {
         ...DEFAULT_SYSTEM_SETTINGS,
         version: SYSTEM_SETTINGS_VERSION,
         localBooksDir: await this.fs.getPrefix('Books'),
+        koreaderSyncDeviceId: uuidv4(),
         globalReadSettings: {
           ...DEFAULT_READSETTINGS,
           ...(this.isMobile ? DEFAULT_MOBILE_READSETTINGS : {}),
diff --git a/apps/readest-app/src/services/constants.ts b/apps/readest-app/src/services/constants.ts
index 1ec46e5b..fed99685 100644
--- a/apps/readest-app/src/services/constants.ts
+++ b/apps/readest-app/src/services/constants.ts
@@ -53,6 +53,15 @@ export const DEFAULT_SYSTEM_SETTINGS: Partial<SystemSettings> = {
   librarySortAscending: false,
   libraryCoverFit: 'crop',
 
+  koreaderSyncServerUrl: 'https://sync.koreader.rocks/', // https://kosync.ak-team.com:3042/
+  koreaderSyncUsername: '',
+  koreaderSyncUserkey: '',
+  koreaderSyncDeviceId: '',
+  koreaderSyncDeviceName: '',
+  koreaderSyncChecksumMethod: 'binary',
+  koreaderSyncStrategy: 'prompt',
+  koreaderSyncPercentageTolerance: 0.00001,
+
   lastSyncedAtBooks: 0,
   lastSyncedAtConfigs: 0,
   lastSyncedAtNotes: 0,
diff --git a/apps/readest-app/src/services/sync/KOSyncClient.ts b/apps/readest-app/src/services/sync/KOSyncClient.ts
new file mode 100644
index 00000000..7e28439d
--- /dev/null
+++ b/apps/readest-app/src/services/sync/KOSyncClient.ts
@@ -0,0 +1,218 @@
+import { md5 } from 'js-md5';
+import { Book } from '@/types/book';
+import { KoreaderSyncChecksumMethod } from '@/types/settings';
+import { getAPIBaseUrl } from '../environment';
+import { KoSyncProxyPayload } from '@/types/kosync';
+
+/**
+ * Interface for KOSync progress response from the server
+ */
+export interface KoSyncProgress {
+  document?: string;
+  progress?: string;
+  percentage?: number;
+  timestamp?: number;
+  device?: string;
+  device_id?: string;
+}
+
+export class KOSyncClient {
+  private serverUrl: string;
+  private username: string;
+  private userkey: string;
+  private checksumMethod: KoreaderSyncChecksumMethod;
+  private deviceId: string;
+  private deviceName: string;
+
+  constructor(
+    serverUrl: string,
+    username: string,
+    userkey: string,
+    checksumMethod: KoreaderSyncChecksumMethod,
+    deviceId: string,
+    deviceName: string,
+  ) {
+    this.serverUrl = serverUrl.replace(/\/$/, '');
+    this.username = username;
+    this.userkey = userkey;
+    this.checksumMethod = checksumMethod;
+    this.deviceId = deviceId;
+    this.deviceName = deviceName;
+  }
+
+  private async request(
+    endpoint: string,
+    options: {
+      method?: 'GET' | 'POST' | 'PUT';
+      body?: BodyInit | null;
+      headers?: HeadersInit;
+      useAuth?: boolean;
+    } = {},
+  ): Promise<Response> {
+    const { method = 'GET', body, headers: additionalHeaders, useAuth = true } = options;
+
+    const headers = new Headers(additionalHeaders || {});
+    if (useAuth) {
+      headers.set('X-Auth-User', this.username);
+      headers.set('X-Auth-Key', this.userkey);
+    }
+
+    const proxyUrl = `${getAPIBaseUrl()}/kosync`;
+
+    const proxyBody: KoSyncProxyPayload = {
+      serverUrl: this.serverUrl,
+      endpoint,
+      method,
+      headers: Object.fromEntries(headers.entries()),
+      body: body ? JSON.parse(body as string) : undefined,
+    };
+
+    return fetch(proxyUrl, {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json',
+      },
+      body: JSON.stringify(proxyBody),
+    });
+  }
+
+  /**
+   * Connects to the KOSync server with authentication
+   * @param username - The username for authentication
+   * @param password - The password for authentication
+   * @returns Promise with success status and optional message
+   */
+  async connect(
+    username: string,
+    password: string,
+  ): Promise<{ success: boolean; message?: string }> {
+    const userkey = md5(password);
+
+    try {
+      const authResponse = await this.request('/users/auth', {
+        method: 'GET',
+        headers: {
+          'X-Auth-User': username,
+          'X-Auth-Key': userkey,
+        },
+      });
+
+      if (authResponse.ok) {
+        return { success: true, message: 'Login successful.' };
+      }
+
+      if (authResponse.status === 401) {
+        const registerResponse = await this.request('/users/create', {
+          method: 'POST',
+          useAuth: false,
+          body: JSON.stringify({ username, password: userkey }),
+        });
+
+        if (registerResponse.ok) {
+          return { success: true, message: 'Registration successful.' };
+        }
+
+        const regError = await registerResponse.json().catch(() => ({}));
+        if (registerResponse.status === 402) {
+          return { success: false, message: 'Invalid credentials.' };
+        }
+        return { success: false, message: regError.message || 'Registration failed.' };
+      }
+
+      const errorBody = await authResponse.json().catch(() => ({}));
+      return {
+        success: false,
+        message: errorBody.message || `Authorization failed with status: ${authResponse.status}`,
+      };
+    } catch (e) {
+      console.error('KOSync connection failed', e);
+      return { success: false, message: (e as Error).message || 'Connection error.' };
+    }
+  }
+
+  /**
+   * Retrieves the reading progress for a specific book from the server
+   * @param book - The book to get progress for
+   * @returns Promise with the progress data or null if not found
+   */
+  async getProgress(book: Book): Promise<KoSyncProgress | null> {
+    if (!this.userkey) return null;
+
+    const documentHash = this.getDocumentDigest(book);
+    if (!documentHash) return null;
+
+    try {
+      const response = await this.request(`/syncs/progress/${documentHash}`);
+
+      if (!response.ok) {
+        console.error(
+          `KOSync: Failed to get progress for ${book.title}. Status: ${response.status}`,
+        );
+        return null;
+      }
+
+      const data = await response.json();
+      return data.document ? data : null;
+    } catch (e) {
+      console.error('KOSync getProgress failed', e);
+      return null;
+    }
+  }
+
+  /**
+   * Updates the reading progress for a specific book on the server
+   * @param book - The book to update progress for
+   * @param progress - The current reading progress position
+   * @param percentage - The reading completion percentage
+   * @returns Promise with boolean indicating success
+   */
+  async updateProgress(book: Book, progress: string, percentage: number): Promise<boolean> {
+    if (!this.userkey) return false;
+
+    const documentHash = this.getDocumentDigest(book);
+    if (!documentHash) return false;
+
+    const payload = {
+      document: documentHash,
+      progress: progress.toString(),
+      percentage,
+      device: this.deviceName,
+      device_id: this.deviceId,
+    };
+
+    try {
+      const response = await this.request('/syncs/progress', {
+        method: 'PUT',
+        body: JSON.stringify(payload),
+      });
+
+      if (!response.ok) {
+        console.error(
+          `KOSync: Failed to update progress for ${book.title}. Status: ${response.status}`,
+        );
+        return false;
+      }
+      return true;
+    } catch (e) {
+      console.error('KOSync updateProgress failed', e);
+      return false;
+    }
+  }
+
+  private getDocumentDigest(book: Book): string | undefined {
+    if (this.checksumMethod === 'filename') {
+      const filename = this.getBaseFilename(book.sourceTitle || book.title);
+      return md5(filename);
+    }
+    return book.hash;
+  }
+
+  private getBaseFilename(fullPath: string): string {
+    // Normalize path by replacing backslashes with forward slashes for cross-platform consistency
+    const normalizedPath = fullPath.replace(/\\/g, '/');
+    // Get the last part of the path and remove the extension
+    const baseName =
+      normalizedPath.split('/').pop()?.split('.').slice(0, -1).join('.') || normalizedPath;
+    return baseName;
+  }
+}
diff --git a/apps/readest-app/src/types/kosync.ts b/apps/readest-app/src/types/kosync.ts
new file mode 100644
index 00000000..bae03022
--- /dev/null
+++ b/apps/readest-app/src/types/kosync.ts
@@ -0,0 +1,11 @@
+/**
+ * Defines the contract for the request body that the client will send
+ * to our API endpoint that acts as a proxy.
+ */
+export interface KoSyncProxyPayload {
+  serverUrl: string;
+  endpoint: string;
+  method: 'GET' | 'POST' | 'PUT';
+  headers: Record<string, string>;
+  body?: unknown;
+}
diff --git a/apps/readest-app/src/types/settings.ts b/apps/readest-app/src/types/settings.ts
index 82cd7663..32b3f1d8 100644
--- a/apps/readest-app/src/types/settings.ts
+++ b/apps/readest-app/src/types/settings.ts
@@ -6,6 +6,9 @@ export type LibraryViewModeType = 'grid' | 'list';
 export type LibrarySortByType = 'title' | 'author' | 'updated' | 'created' | 'size' | 'format';
 export type LibraryCoverFitType = 'crop' | 'fit';
 
+export type KoreaderSyncChecksumMethod = 'binary' | 'filename';
+export type KoreaderSyncStrategy = 'prompt' | 'silent' | 'send' | 'receive' | 'disabled';
+
 export interface ReadSettings {
   sideBarWidth: string;
   isSideBarPinned: boolean;
@@ -40,6 +43,15 @@ export interface SystemSettings {
   librarySortAscending: boolean;
   libraryCoverFit: LibraryCoverFitType;
 
+  koreaderSyncServerUrl: string;
+  koreaderSyncUsername: string;
+  koreaderSyncUserkey: string;
+  koreaderSyncDeviceId: string;
+  koreaderSyncDeviceName: string;
+  koreaderSyncChecksumMethod: KoreaderSyncChecksumMethod;
+  koreaderSyncStrategy: KoreaderSyncStrategy;
+  koreaderSyncPercentageTolerance: number;
+
   lastSyncedAtBooks: number;
   lastSyncedAtConfigs: number;
   lastSyncedAtNotes: number;
diff --git a/apps/readest-app/src/utils/debounce.ts b/apps/readest-app/src/utils/debounce.ts
index c72dc81b..5181f5b0 100644
--- a/apps/readest-app/src/utils/debounce.ts
+++ b/apps/readest-app/src/utils/debounce.ts
@@ -5,22 +5,24 @@ interface DebounceOptions {
 /**
  * Debounces a function by waiting `delay` ms after the last call before executing it.
  * If `emitLast` is false, it cancels the call instead of delaying it.
+ *
+ * @returns A debounced function with additional `flush` and `cancel` methods.
  */
 export const debounce = <T extends (...args: Parameters<T>) => void | Promise<void>>(
   func: T,
   delay: number,
   options: DebounceOptions = { emitLast: true },
-): ((...args: Parameters<T>) => void) => {
+): ((...args: Parameters<T>) => void) & { flush: () => void; cancel: () => void } => {
   let timeout: ReturnType<typeof setTimeout> | null = null;
   let lastArgs: Parameters<T> | null = null;
 
-  return (...args: Parameters<T>): void => {
+  const debounced = (...args: Parameters<T>): void => {
+    lastArgs = args;
     if (timeout) {
       clearTimeout(timeout);
     }
 
     if (options.emitLast) {
-      lastArgs = args;
       timeout = setTimeout(() => {
         if (lastArgs) {
           func(...(lastArgs as Parameters<T>));
@@ -35,4 +37,31 @@ export const debounce = <T extends (...args: Parameters<T>) => void | Promise<vo
       }, delay);
     }
   };
+
+  /**
+   * Immediately executes the last pending debounced function call.
+   */
+  debounced.flush = () => {
+    if (timeout) {
+      clearTimeout(timeout);
+      timeout = null;
+      if (lastArgs) {
+        func(...(lastArgs as Parameters<T>));
+        lastArgs = null;
+      }
+    }
+  };
+
+  /**
+   * Cancels the pending debounced function call.
+   */
+  debounced.cancel = () => {
+    if (timeout) {
+      clearTimeout(timeout);
+      timeout = null;
+      lastArgs = null;
+    }
+  };
+
+  return debounced;
 };
diff --git a/apps/readest-app/src/utils/xcfi.ts b/apps/readest-app/src/utils/xcfi.ts
index 5d3da004..055c869c 100644
--- a/apps/readest-app/src/utils/xcfi.ts
+++ b/apps/readest-app/src/utils/xcfi.ts
@@ -3,6 +3,7 @@
  * Converts between Readest (foliate-js) CFI format and KOReader CREngine XPointer format
  */
 
+import { BookDoc } from '@/libs/document';
 import { parse, fake, collapse, fromRange, toRange, toElement } from 'foliate-js/epubcfi.js';
 
 type XPointer = {
@@ -498,3 +499,23 @@ export class XCFI {
     return !inlineElements.has(tagName);
   }
 }
+
+export const getCFIFromXPointer = async (
+  xpointer: string,
+  doc: Document,
+  index: number,
+  bookDoc?: BookDoc,
+) => {
+  const xSpineIndex = XCFI.extractSpineIndex(xpointer);
+  let converter: XCFI;
+  if (index === xSpineIndex) {
+    converter = new XCFI(doc, index || 0);
+  } else {
+    const doc = await bookDoc?.sections?.[xSpineIndex]?.createDocument();
+    if (!doc) throw new Error('Failed to load document for XPointer conversion.');
+    converter = new XCFI(doc, xSpineIndex || 0);
+  }
+
+  const cfi = converter.xPointerToCFI(xpointer);
+  return cfi;
+};
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index e9b20c2f..46eab999 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -206,6 +206,9 @@ importers:
       tinycolor2:
         specifier: ^1.6.0
         version: 1.6.0
+      uuid:
+        specifier: ^11.1.0
+        version: 11.1.0
       zod:
         specifier: ^4.0.8
         version: 4.0.10
@@ -255,6 +258,9 @@ importers:
       '@types/tinycolor2':
         specifier: ^1.4.6
         version: 1.4.6
+      '@types/uuid':
+        specifier: ^10.0.0
+        version: 10.0.0
       '@vitejs/plugin-react':
         specifier: ^4.7.0
         version: 4.7.0(vite@7.0.6(@types/node@22.15.31)(jiti@1.21.6)(terser@5.43.1)(yaml@2.7.0))
@@ -3160,6 +3166,9 @@ packages:
   '@types/trusted-types@2.0.7':
     resolution: {integrity: sha512-ScaPdn1dQczgbl0QFTeTOmVHFULt394XJgOQNoyVhZ6r2vLnMLJfBPd53SB52T/3G36VI1/g2MZaX0cwDuXsfw==}
 
+  '@types/uuid@10.0.0':
+    resolution: {integrity: sha512-7gqG38EyHgyP1S+7+xomFtL+ZNHcKv6DwNaCZmJmo1vgMugyF3TCnXVg4t1uk89mLNwnLtnY3TpOpCOyp1/xHQ==}
+
   '@types/uuid@9.0.8':
     resolution: {integrity: sha512-jg+97EGIcY9AGHJJRaaPVgetKDsrTgbRjQ5Msgjh/DQKEFl0DtyRr/VCOyD1T2R1MNeWPK/u7JoGhlDZnKBAfA==}
 
@@ -6519,6 +6528,10 @@ packages:
     resolution: {integrity: sha512-pMZTvIkT1d+TFGvDOqodOclx0QWkkgi6Tdoa8gC8ffGAAqz9pzPTZWAybbsHHoED/ztMtkv/VoYTYyShUn81hA==}
     engines: {node: '>= 0.4.0'}
 
+  uuid@11.1.0:
+    resolution: {integrity: sha512-0/A9rDy9P7cJ+8w1c9WD9V//9Wj15Ce2MPz8Ri6032usz+NfePxx5AcN3bN+r6ZL6jEo066/yNYB3tn4pQEx+A==}
+    hasBin: true
+
   uuid@9.0.1:
     resolution: {integrity: sha512-b+1eJOlsR9K8HJpow9Ok3fiWOWSIcIzXodvv0rQjVoOVNpWMpxf1wZNpt4y9h10odCNrqnYp1OBzRktckBe3sA==}
     hasBin: true
@@ -10844,6 +10857,8 @@ snapshots:
 
   '@types/trusted-types@2.0.7': {}
 
+  '@types/uuid@10.0.0': {}
+
   '@types/uuid@9.0.8': {}
 
   '@types/ws@8.18.1':
@@ -14473,6 +14488,8 @@ snapshots:
 
   utils-merge@1.0.1: {}
 
+  uuid@11.1.0: {}
+
   uuid@9.0.1: {}
 
   v8-compile-cache-lib@3.0.1: