---
title: 伪类
slug: Web/CSS/Pseudo-classes
tags:
  - CSS
  - CSS 参考
  - 进阶
  - 选择器
translation_of: Web/CSS/Pseudo-classes
---
<div>{{CSSRef}}</div>

<p>CSS <strong><dfn>伪类</dfn></strong> 是添加到选择器的关键字，指定要选择的元素的特殊状态。例如，{{ cssxref(":hover") }} 可被用于在用户将鼠标悬停在按钮上时改变按钮的颜色。</p>

<pre class="brush: css no-line-numbers">/* 所有用户指针悬停的按钮 */
button:hover {
  color: blue;
}
</pre>

<p>伪类连同伪元素一起，他们允许你不仅仅是根据文档 DOM 树中的内容对元素应用样式，而且还允许你根据诸如像导航历史这样的外部因素来应用样式（例如 {{ cssxref(":visited") }}），同样的，可以根据内容的状态（例如在一些表单元素上的 {{ cssxref(":checked") }}），或者鼠标的位置（例如 {{ cssxref(":hover") }} 让你知道是否鼠标在一个元素上悬浮）来应用样式。</p>

<div class="blockIndicator note">
<p><strong>注意：</strong> 与伪类相反，{{cssxref("pseudo-elements")}} 可被用于为一个元素的 <em>特定部分</em> 应用样式。</p>
</div>

<h2 id="语法">语法</h2>

<pre class="syntaxbox">selector:pseudo-class {
  property: value;
}</pre>

<p>类似于普通的类，你可以在一个选择器中同时一起写多个伪类。</p>

<h2 id="标准伪类索引">标准伪类索引</h2>

<div class="index" id="索引">
<ul>
 <li>{{CSSxRef(":active")}}</li>
 <li>{{CSSxRef(":any-link")}} {{Experimental_Inline}}</li>
 <li>{{CSSxRef(":blank")}} {{Experimental_Inline}}</li>
 <li>{{CSSxRef(":checked")}}</li>
 <li>{{CSSxRef(":current")}} {{Experimental_Inline}}</li>
 <li>{{CSSxRef(":default")}}</li>
 <li>{{CSSxRef(":defined")}}</li>
 <li>{{CSSxRef(":dir", ":dir()")}} {{Experimental_Inline}}</li>
 <li>{{CSSxRef(":disabled")}}</li>
 <li>{{CSSxRef(":drop")}} {{Experimental_Inline}}</li>
 <li>{{CSSxRef(":empty")}}</li>
 <li>{{CSSxRef(":enabled")}}</li>
 <li>{{CSSxRef(":first")}}</li>
 <li>{{CSSxRef(":first-child")}}</li>
 <li>{{CSSxRef(":first-of-type")}}</li>
 <li>{{CSSxRef(":fullscreen")}} {{Experimental_Inline}}</li>
 <li>{{CSSxRef(":future")}} {{Experimental_Inline}}</li>
 <li>{{CSSxRef(":focus")}}</li>
 <li>{{CSSxRef(":focus-visible")}} {{Experimental_Inline}}</li>
 <li>{{CSSxRef(":focus-within")}}</li>
 <li>{{CSSxRef(":has", ":has()")}} {{Experimental_Inline}}</li>
 <li>{{CSSxRef(":host")}}</li>
 <li>{{CSSxRef(":host()")}}</li>
 <li>{{CSSxRef(":host-context()")}} {{Experimental_Inline}}</li>
 <li>{{CSSxRef(":hover")}}</li>
 <li>{{CSSxRef(":indeterminate")}}</li>
 <li>{{CSSxRef(":in-range")}}</li>
 <li>{{CSSxRef(":invalid")}}</li>
 <li>{{CSSxRef(":is", ":is()")}} {{Experimental_Inline}}</li>
 <li>{{CSSxRef(":lang", ":lang()")}}</li>
 <li>{{CSSxRef(":last-child")}}</li>
 <li>{{CSSxRef(":last-of-type")}}</li>
 <li>{{CSSxRef(":left")}}</li>
 <li>{{CSSxRef(":link")}}</li>
 <li>{{CSSxRef(":local-link")}} {{Experimental_Inline}}</li>
 <li>{{CSSxRef(":not", ":not()")}}</li>
 <li>{{CSSxRef(":nth-child", ":nth-child()")}}</li>
 <li>{{CSSxRef(":nth-col", ":nth-col()")}} {{Experimental_Inline}}</li>
 <li>{{CSSxRef(":nth-last-child", ":nth-last-child()")}}</li>
 <li>{{CSSxRef(":nth-last-col", ":nth-last-col()")}} {{Experimental_Inline}}</li>
 <li>{{CSSxRef(":nth-last-of-type", ":nth-last-of-type()")}}</li>
 <li>{{CSSxRef(":nth-of-type", ":nth-of-type()")}}</li>
 <li>{{CSSxRef(":only-child")}}</li>
 <li>{{CSSxRef(":only-of-type")}}</li>
 <li>{{CSSxRef(":optional")}}</li>
 <li>{{CSSxRef(":out-of-range")}}</li>
 <li>{{CSSxRef(":past")}} {{Experimental_Inline}}</li>
 <li>{{CSSxRef(":placeholder-shown")}} {{Experimental_Inline}}</li>
 <li>{{CSSxRef(":read-only")}}</li>
 <li>{{CSSxRef(":read-write")}}</li>
 <li>{{CSSxRef(":required")}}</li>
 <li>{{CSSxRef(":right")}}</li>
 <li>{{CSSxRef(":root")}}</li>
 <li>{{CSSxRef(":scope")}}</li>
 <li>{{CSSxRef(":target")}}</li>
 <li>{{CSSxRef(":target-within")}} {{Experimental_Inline}}</li>
 <li>{{CSSxRef(":user-invalid")}} {{Experimental_Inline}}</li>
 <li>{{CSSxRef(":valid")}}</li>
 <li>{{CSSxRef(":visited")}}</li>
 <li>{{CSSxRef(":where", ":where()")}} {{Experimental_Inline}}</li>
</ul>
</div>

<h2 id="规范">规范</h2>

<table class="standard-table">
 <thead>
  <tr>
   <th scope="col">规范</th>
   <th scope="col">状态</th>
   <th scope="col">备注</th>
  </tr>
 </thead>
 <tbody>
  <tr>
   <td>
    <table>
     <tbody>
      <tr>
       <td>{{SpecName("Fullscreen")}}</td>
       <td>{{Spec2("Fullscreen")}}</td>
       <td>Defined <code>:fullscreen</code>.</td>
      </tr>
      <tr>
       <td>{{SpecName("HTML WHATWG", "#pseudo-classes")}}</td>
       <td>{{Spec2("HTML WHATWG")}}</td>
       <td>Defines when particular selectors match HTML elements.</td>
      </tr>
      <tr>
       <td>{{SpecName("CSS4 Selectors")}}</td>
       <td>{{Spec2("CSS4 Selectors")}}</td>
       <td>Defined <code>:any-link</code>, <code>:blank</code>, <code>:local-link</code>, <code>:scope</code>, <code>:drop</code>, <code>:current</code>, <code>:past</code>, <code>:future</code>, <code>:placeholder-shown</code>, <code>:user-invalid</code>, <code>:nth-col()</code>, <code>:nth-last-col()</code>, <code>:is()</code> and <code>:where()</code>.<br>
        Changed <code>:empty</code> to behave like {{CSSxRef(":-moz-only-whitespace")}} {{Non-standard_Inline}}.<br>
        No significant change for other pseudo-classes defined in {{SpecName("CSS3 Selectors")}} and {{SpecName("HTML5 W3C")}} (though semantic meaning not taken over).</td>
      </tr>
      <tr>
       <td>{{SpecName("HTML5 W3C")}}</td>
       <td>{{Spec2("HTML5 W3C")}}</td>
       <td>Copies the relevant section from the canonical (WHATWG) HTML spec.</td>
      </tr>
      <tr>
       <td>{{SpecName("CSS3 Basic UI")}}</td>
       <td>{{Spec2("CSS3 Basic UI")}}</td>
       <td>Defined <code>:default</code>, <code>:valid</code>, <code>:invalid</code>, <code>:in-range</code>, <code>:out-of-range</code>, <code>:required</code>, <code>:optional</code>, <code>:read-only</code> and <code>:read-write</code>, but without the associated semantic meaning.</td>
      </tr>
      <tr>
       <td>{{SpecName("CSS3 Selectors")}}</td>
       <td>{{Spec2("CSS3 Selectors")}}</td>
       <td>Defined <code>:target</code>, <code>:root</code>, <code>:nth-child()</code>, <code>:nth-last-of-child()</code>, <code>:nth-of-type()</code>, <code>:nth-last-of-type()</code>, <code>:last-child</code>, <code>:first-of-type</code>, <code>:last-of-type</code>, <code>:only-child</code>, <code>:only-of-type</code>, <code>:empty</code> and <code>:not()</code>.<br>
        Defined the syntax of <code>:enabled</code>, <code>:disabled</code>, <code>:checked</code>, and <code>:indeterminate</code>, but without the associated semantic meaning.<br>
        No significant change for pseudo-classes defined in {{SpecName('CSS2.1')}}.</td>
      </tr>
      <tr>
       <td>{{SpecName("CSS2.1")}}</td>
       <td>{{Spec2("CSS2.1")}}</td>
       <td>Defined <code>:lang()</code>, <code>:first-child</code>, <code>:hover</code>, and <code>:focus</code>.<br>
        No significant change for pseudo-classes defined in {{SpecName('CSS1')}}.</td>
      </tr>
      <tr>
       <td>{{SpecName("CSS1")}}</td>
       <td>{{Spec2("CSS1")}}</td>
       <td>Defined <code>:link</code>, <code>:visited</code> and <code>:active</code>, but without the associated semantic meaning.</td>
      </tr>
     </tbody>
    </table>
   </td>
  </tr>
 </tbody>
</table>

<h2 id="参见">参见</h2>

<ul>
 <li>{{ cssxref("pseudo-elements") }}</li>
</ul>