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left CSS property participates in specifying the horizontal position of a positioned element . It has no effect on non-positioned elements.

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

句法 

/* <length> values */
left: 3px;
left: 2.4em;
/* <percentage>s of the width of the containing block */
left: 10%;
/* Keyword value */
left: auto;
/* Global values */
left: inherit;
left: initial;
left: unset;

值

<length>
A negative, null, or positive <length> that represents:
  • for absolutely positioned elements , the distance to the left edge of the containing block.
  • for relatively positioned elements , the distance that the element is moved to the right of its normal position.
<percentage>
A <percentage> of the containing block's width.
auto
Specifies that:
  • for absolutely positioned elements , the position of the element is based on the right property, while width: auto is treated as a width based on the content; or if right is also auto , the element is positioned where it should horizontally be positioned if it were a static element.
  • for relatively positioned elements , the distance of the element from its normal position is based on the right property; or if right is also auto , the element is not moved horizontally at all.
inherit
Specifies that the value is the same as the computed value from its parent element (which might not be its containing block). This computed value is then handled as if it were a <length> , <percentage> ，或 auto 关键词。

描述

The effect of left depends on how the element is positioned (i.e., the value of the position property):

  • When position is set to absolute or fixed ， left property specifies the distance between the element's left edge and the left edge of its containing block. (The containing block is the ancestor to which the element is relatively positioned.)
  • When position is set to relative ， left property specifies the distance the element's left edge is moved to the right from its normal position.
  • When position is set to sticky ， left property is used to compute the sticky-constraint rectangle.
  • When position is set to static ， left property has no effect .

When both left and right are defined, and width constraints don't prevent it, the element will stretch to satisfy both. If the element cannot stretch to satisfy both, the position of the element is overspecified . When this is the case, the left value has precedence when the container is left-to-right; the right value has precedence when the container is right-to-left.

形式定义

初始值 auto
适用于 positioned elements
继承 no
百分比 refer to the width of the containing block
计算值 if specified as a length, the corresponding absolute length; if specified as a percentage, the specified value; otherwise, auto
动画类型 a length , percentage or calc();

形式句法 

<length> | <percentage> | auto

范例

Positioning elements

HTML 

<div id="wrap">
  <div id="example_1">
    <pre>
      position: absolute;
      left: 20px;
      top: 20px;
    </pre>
    <p>The only containing element for this div is the main window, so it positions itself in relation to it.</p>
  </div>
  <div id="example_2">
    <pre>
      position: relative;
      top: 0;
      right: 0;
    </pre>
    <p>Relative position in relation to its siblings.</p>
  </div>
  <div id="example_3">
    <pre>
      float: right;
      position: relative;
      top: 20px;
      left: 20px;
    </pre>
    <p>Relative to its sibling div above, but removed from flow of content.</p>
    <div id="example_4">
      <pre>
        position: absolute;
        bottom: 10px;
        right: 20px;
      </pre>
      <p>Absolute position inside of a parent with relative position</p>
    </div>
    <div id="example_5">
      <pre>
        position: absolute;
        right: 0;
        left: 0;
        top: 200px;
      </pre>
      <p>Absolute position with both left and right declared</p> </div>
  </div>
</div>

CSS 

#wrap {
  width: 700px;
  margin: 0 auto;
  background: #5C5C5C;
}
pre {
  white-space: pre;
  white-space: pre-wrap;
  white-space: pre-line;
  word-wrap: break-word;
}
#example_1 {
  width: 200px;
  height: 200px;
  position: absolute;
  left: 20px;
  top: 20px;
  background-color: #D8F5FF;
}
#example_2 {
  width: 200px;
  height: 200px;
  position: relative;
  top: 0;
  right: 0;
  background-color: #C1FFDB;
}
#example_3 {
  width: 600px;
  height: 400px;
  position: relative;
  top: 20px;
  left: 20px;
  background-color: #FFD7C2;
}
#example_4 {
  width:200px;
  height:200px;
  position:absolute;
  bottom:10px;
  right:20px;
  background-color:#FFC7E4;
}
#example_5 {
  position: absolute;
  right: 0;
  left: 0;
  top: 100px;
  background-color: #D7FFC2;
}

结果

规范

规范 状态 注释
CSS Positioned Layout Module Level 3
The definition of 'left' in that specification. 		工作草案 Adds behavior for sticky positioning.
CSS Level 2 (Revision 1)
The definition of 'left' in that specification. 		推荐 初始定义。

浏览器兼容性

The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request. 更新 GitHub 上的兼容性数据
Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari Android webview Chrome for Android Firefox for Android Opera for Android Safari on iOS Samsung Internet
left Chrome 完整支持 1 Edge 完整支持 12 Firefox 完整支持 1 IE 完整支持 5.5 Opera 完整支持 5 Safari 完整支持 1 WebView Android 完整支持 1 Chrome Android 完整支持 18 Firefox Android 完整支持 4 Opera Android 完整支持 14 Safari iOS 完整支持 1 Samsung Internet Android 完整支持 1.0

图例

完整支持

完整支持

另请参阅

元数据

  • 最后修改：
  1. CSS
  2. CSS 参考
  3. CSS Positioning
  4. 指南
    1. Understanding CSS z-index
  5. 特性
    1. bottom
    2. clear
    3. float
    4. left
    5. position
    6. right
    7. top
    8. z-index