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noUnknownPseudoElement

src/content/docs/linter/rules/no-unknown-pseudo-element.mdx

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import { Tabs, TabItem } from '@astrojs/starlight/components';

<Tabs> <TabItem label="CSS" icon="seti:css"> ## Summary - Rule available since: `v1.8.0` - Diagnostic Category: [`lint/correctness/noUnknownPseudoElement`](/reference/diagnostics#diagnostic-category) - This rule is **recommended**, meaning it is enabled by default. - This rule doesn't have a fix. - The default severity of this rule is [**error**](/reference/diagnostics#error). - Sources: - Same as [`selector-pseudo-element-no-unknown`](https://github.com/stylelint/stylelint/blob/main/lib/rules/selector-pseudo-element-no-unknown/README.md)

How to configure

json
{
	"linter": {
		"rules": {
			"correctness": {
				"noUnknownPseudoElement": "error"
			}
		}
	}
}

Description

Disallow unknown pseudo-element selectors.

For details on known CSS pseudo-elements, see the MDN web docs.

This rule ignores vendor-prefixed pseudo-element selectors.

Examples

Invalid

css
a::pseudo {}
<pre class="language-text"><code class="language-text">code-block.css:1:4 <a href="https://biomejs.dev/linter/rules/no-unknown-selector-pseudo-element">lint/correctness/noUnknownPseudoElement</a> ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ <strong><span style="color: Tomato;">✖</span></strong> <span style="color: Tomato;">Unexpected unknown pseudo-elements: </span><span style="color: Tomato;"><strong>pseudo</strong></span> <strong><span style="color: Tomato;">&gt;</span></strong> <strong>1 │ </strong>a::pseudo &#123;&#125; <strong> │ </strong> <strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong> <strong>2 │ </strong> <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">See </span><span style="color: lightgreen;"><a href="https://developer.mozilla.org/en-US/docs/Web/CSS/Pseudo-elements#list_of_pseudo-elements">MDN web docs</a></span><span style="color: lightgreen;"> for more details.</span> <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">Use a known pseudo-elements instead, such as:</span> - after - backdrop - before - etc. </code></pre>
css
a::PSEUDO {}
<pre class="language-text"><code class="language-text">code-block.css:1:4 <a href="https://biomejs.dev/linter/rules/no-unknown-selector-pseudo-element">lint/correctness/noUnknownPseudoElement</a> ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ <strong><span style="color: Tomato;">✖</span></strong> <span style="color: Tomato;">Unexpected unknown pseudo-elements: </span><span style="color: Tomato;"><strong>PSEUDO</strong></span> <strong><span style="color: Tomato;">&gt;</span></strong> <strong>1 │ </strong>a::PSEUDO &#123;&#125; <strong> │ </strong> <strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong> <strong>2 │ </strong> <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">See </span><span style="color: lightgreen;"><a href="https://developer.mozilla.org/en-US/docs/Web/CSS/Pseudo-elements#list_of_pseudo-elements">MDN web docs</a></span><span style="color: lightgreen;"> for more details.</span> <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">Use a known pseudo-elements instead, such as:</span> - after - backdrop - before - etc. </code></pre>
css
a::element {}
<pre class="language-text"><code class="language-text">code-block.css:1:4 <a href="https://biomejs.dev/linter/rules/no-unknown-selector-pseudo-element">lint/correctness/noUnknownPseudoElement</a> ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ <strong><span style="color: Tomato;">✖</span></strong> <span style="color: Tomato;">Unexpected unknown pseudo-elements: </span><span style="color: Tomato;"><strong>element</strong></span> <strong><span style="color: Tomato;">&gt;</span></strong> <strong>1 │ </strong>a::element &#123;&#125; <strong> │ </strong> <strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong> <strong>2 │ </strong> <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">See </span><span style="color: lightgreen;"><a href="https://developer.mozilla.org/en-US/docs/Web/CSS/Pseudo-elements#list_of_pseudo-elements">MDN web docs</a></span><span style="color: lightgreen;"> for more details.</span> <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">Use a known pseudo-elements instead, such as:</span> - after - backdrop - before - etc. </code></pre>

Valid

css
a:before {}
css
a::before {}
css
::selection {}
css
input::-moz-placeholder {}

Options

ignore

A list of unknown pseudo-element names to ignore (case-insensitive).

json
{
	"linter": {
		"rules": {
			"correctness": {
				"noUnknownPseudoElement": {
					"options": {
						"ignore": [
							"custom-pseudo-element"
						]
					}
				}
			}
		}
	}
}

Valid

css
::custom-pseudo-element {}
</TabItem> </Tabs>