---
title: margin-left
slug: Web/CSS/margin-left
translation_of: Web/CSS/margin-left
---
<div>{{CSSRef()}}</div>

<h2 id="Summary" name="Summary">Summary</h2>

<p><img alt="Area on which CSS margin-left apply" src="/files/4039/margin-left.svg" style="border-style: solid; border-width: 1px; float: left; margin-bottom: 2em; margin-right: 1em;"><span class="seoSummary"><strong><code>margin-left</code></strong>  属性 设置与元素相关联的盒子模型的左外边距。这个值可以为负值。</span></p>

<p><span class="seoSummary">竖直排列相邻的两个盒子模型的外边距会重叠 <em><a href="/en-US/docs/CSS/margin_collapsing" title="/en-US/docs/CSS/margin_collapsing">margin collapsing</a>。</em></span></p>

<p><span class="seoSummary">在长度(width)被约束这种极少情况下，( <code>即当所有的宽度，左边界，边界，填充内容区域和边缘都被定义</code>), 左边界<code>会被忽略，</code>如果被制定为auto值，会有相同的计算值。</span></p>

<p>{{cssinfo()}}</p>

<h2 id="Syntax" name="Syntax">Syntax</h2>

<pre class="brush:css">/* &lt;length&gt; values */
margin-left: 10px;  /* 绝对长度 */
margin-left: 1em;   /* 相对于字号的长度 */
margin-left: 5%;    /* 相对最近块元素的宽度 */

/* Keyword values */
margin-left: auto;

/* Global values */
margin-left: inherit;
margin-left: initial;
margin-left: unset;
</pre>

<h3 id="Values" name="Values">Values</h3>

<dl>
 <dt><code>&lt;length&gt;</code></dt>
 <dd>一个固定宽度 {{cssxref("&lt;length&gt;")}} 值 : 可以是一个绝对宽度, e.g. in <code>px</code>, 也可以是个相对宽度, e.g. in <code>em</code>, 或者相对视窗的大小, e.g. in <code>vh</code>.</dd>
 <dt><code>&lt;percentage&gt;</code></dt>
 <dd>百分比值 {{cssxref("&lt;percentage&gt;")}} 最近的块容器的宽度 <em>width</em> .</dd>
 <dt><code>auto</code></dt>
 <dd>auto关键词表示在当前布局模式下，浏览器根据接收的左边距自动计算出外边距。如果有几组margin-left和margin-right 设置为auto，那么最后计算的空间分布，会根据display，float，position属性，自动生成以下几种情况：
 <table class="standard-table">
  <thead>
   <tr>
    <th scope="col">Value of {{cssxref("display")}}</th>
    <th scope="col">Value of {{cssxref("float")}}</th>
    <th scope="col">Value of {{cssxref("position")}}</th>
    <th scope="col">Computed value of <code>auto</code></th>
    <th scope="col">Comment</th>
   </tr>
  </thead>
  <tbody>
   <tr>
    <th><code>inline</code>, <code>inline-block</code>, <code>inline-table</code></th>
    <th><em>any</em></th>
    <th><code>static</code> or <code>relative</code></th>
    <td><code>0</code></td>
    <td>Inline layout mode</td>
   </tr>
   <tr>
    <th><code>block</code>, <code>inline</code>, <code>inline-block</code>, <code>block</code>, <code>table</code>, <code>inline-table</code>, <code>list-item</code>, <code>table-caption</code></th>
    <th><em>any</em></th>
    <th><code>static</code> or <code>relative</code></th>
    <td><code>0</code>, 除非<code>margin-left</code>和   <code>margin-right同时都设置为auto</code>. 这样的话，元素就被设置为基于父元素居中。</td>
    <td>Block layout mode</td>
   </tr>
   <tr>
    <th><code>block</code>, <code>inline</code>, <code>inline-block</code>, <code>block</code>, <code>table</code>, <code>inline-table</code>, <code>list-item</code>, <code>table-caption</code></th>
    <th><code>left</code> or <code>right</code></th>
    <th><code>static</code> or <code>relative</code></th>
    <td><code>0</code></td>
    <td>Block layout mode (floating element)</td>
   </tr>
   <tr>
    <th><em>any </em><code>table-*</code><em>, except </em><code>table-caption</code></th>
    <th><em>any</em></th>
    <th><em>any</em></th>
    <td><code>0</code></td>
    <td>Internal <code>table-*</code> elements don't have margins, use {{ cssxref("border-spacing") }} instead</td>
   </tr>
   <tr>
    <th><em>any, except <code>flex</code>,</em> <code>inline-flex</code><em>, or </em><code>table-*</code></th>
    <th><em>any</em></th>
    <th><em><code>fixed</code></em> or <code>absolute</code></th>
    <td><code>0</code>, except if both <code>margin-left</code> and <code>margin-right</code> are set to <code>auto</code>. In this case, it is set to the value centering the border area inside the available <code>width</code>, if fixed.</td>
    <td>Absolutely positioned layout mode</td>
   </tr>
   <tr>
    <th><code>flex</code>, <code>inline-flex</code></th>
    <th><em>any</em></th>
    <th><em>any</em></th>
    <td>
     <p>在水平方向上有空余空间的情况下，空余的空间会被平均分给水平方向上写有margin-left:auto属性的元素的外边距</p>
    </td>
    <td>Flexbox layout mode</td>
   </tr>
  </tbody>
 </table>
 </dd>
</dl>

<h3 id="Formal_syntax">Formal syntax</h3>

{{csssyntax()}}

<h2 id="Examples" name="Examples">Examples</h2>

<pre>.content { margin-left:   5%; }
.sidebox { margin-left: 10px; }
.logo    { margin-left: -5px; }
</pre>

<h2 id="Specifications" name="Specifications">Specifications</h2>

<table class="standard-table">
 <thead>
  <tr>
   <th scope="col">Specification</th>
   <th scope="col">Status</th>
   <th scope="col">Comment</th>
  </tr>
 </thead>
 <tbody>
  <tr>
   <td>{{SpecName('CSS3 Box', '#the-margin', 'margin-left')}}</td>
   <td>{{Spec2('CSS3 Box')}}</td>
   <td>No significant change from CSS 2.1.</td>
  </tr>
  <tr>
   <td>{{SpecName('CSS3 Transitions', '#animatable-css', 'margin-left')}}</td>
   <td>{{Spec2('CSS3 Transitions')}}</td>
   <td>Defines <code>margin-left</code> as animatable.</td>
  </tr>
  <tr>
   <td>{{SpecName('CSS3 Flexbox', '#item-margins', 'margin-left')}}</td>
   <td>{{Spec2('CSS3 Flexbox')}}</td>
   <td>Defines the behavior of <code>margin-left</code> on flex items.</td>
  </tr>
  <tr>
   <td>{{SpecName('CSS2.1', 'box.html#margin-properties', 'margin-left')}}</td>
   <td>{{Spec2('CSS2.1')}}</td>
   <td>Like in CSS1, but removes its effect on inline elements.</td>
  </tr>
  <tr>
   <td>{{SpecName('CSS1', '#margin-left', 'margin-left')}}</td>
   <td>{{Spec2('CSS1')}}</td>
   <td>Initial definition</td>
  </tr>
 </tbody>
</table>

<h2 id="Browser_Compatibility" name="Browser_Compatibility">Browser compatibility</h2>

{{Compat("css.properties.margin-left")}}