@name Invalid Shadow DOM selector
@category compiler
@shortDescription Component selector does not match shadow DOM requirements

@description

The selector of a component using `ViewEncapsulation.ShadowDom` doesn't match the custom element tag name requirements.

In order for a tag name to be considered a valid custom element name, it has to:

*   Be in lower case.
*   Contain a hyphen.
*   Start with a letter \(a-z\).

@debugging
Rename your component's selector so that it matches the requirements.

**Before:**

<code-example format="typescript" language="typescript">

&commat;Component({
  selector: 'comp',
  encapsulation: ViewEncapsulation.ShadowDom
  &hellip;
})

</code-example>

**After:**

<code-example format="typescript" language="typescript">

&commat;Component({
  selector: 'app-comp',
  encapsulation: ViewEncapsulation.ShadowDom
  &hellip;
})

</code-example>