left - CSS: Cascading Style Sheets 编辑

The 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.

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.

Syntax

/* <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;

Values

<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>, or the auto keyword.

Description

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, the 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, the 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, the left property is used to compute the sticky-constraint rectangle.
• When position is set to static, the 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.

Formal definition

Initial value	auto
Applies to	positioned elements
Inherited	no
Percentages	refer to the width of the containing block
Computed value	if specified as a length, the corresponding absolute length; if specified as a percentage, the specified value; otherwise, auto
Animation type	a length, percentage or calc();

Formal syntax

<length> | <percentage> | auto

Examples

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;
}

Result

Specifications

Specification	Status	Comment
CSS Positioned Layout Module Level 3 The definition of 'left' in that specification.	Working Draft	Adds behavior for sticky positioning.
CSS Level 2 (Revision 1) The definition of 'left' in that specification.	Recommendation	Initial definition.

Browser compatibility

BCD tables only load in the browser

See also

• inset, the shorthand for all related properties: top, bottom, left, and right
• The mapped logical properties: inset-block-start, inset-block-end, inset-inline-start, and inset-inline-end and the shorthands inset-block and inset-inline
• position