`title.content.html`

Default: error
Plugin: title

The title has no HTML tags in its text.

Why: A <title> holds plain text. Tags inside it show up as literal text, such as <b>, in search results and browser tabs. Entities such as & are fine.

Only the tags of HTML elements, comments, and declarations count. A title can name a tag that no HTML element has, such as <svelte:head> or <my-element>.

When off: titles with tags pass.

<!-- ✗ Fails -->
<title>Fresh <b>bread</b></title>

<!-- ✓ Passes -->
<title>Fish &amp; Chips</title>
<title>The &lt;svelte:head&gt; element</title>

References

HTML spec: The title element: The title is plain text.
Google: Title links: Google uses the title text for the title link in results.