`bottom` CSS property

The bottom CSS property participates in setting the vertical position of a positioned element. This inset property has no effect on non-positioned elements.

Try it

bottom: 0;

bottom: 4em;

bottom: 10%;

bottom: 20px;

<section id="default-example">
  <div class="example-container">
    <div id="example-element">I am absolutely positioned.</div>
    <p>
      As much mud in the streets as if the waters had but newly retired from the
      face of the earth, and it would not be wonderful to meet a Megalosaurus,
      forty feet long or so, waddling like an elephantine lizard up Holborn
      Hill.
    </p>
  </div>
</section>

.example-container {
  border: 0.75em solid;
  padding: 0.75em;
  text-align: left;
  position: relative;
  width: 100%;
  min-height: 200px;
}

#example-element {
  background-color: #264653;
  border: 4px solid #ffb500;
  color: white;
  position: absolute;
  width: 140px;
  height: 60px;
}

Syntax

css

/* <length> values */
bottom: 3px;
bottom: 2.4em;
bottom: calc(anchor(--my-anchor 50%) + 5px);
bottom: anchor-size(width);

/* <percentage>s of the height of the containing block */
bottom: 10%;

/* Keyword value */
bottom: auto;

/* Global values */
bottom: inherit;
bottom: initial;
bottom: revert;
bottom: revert-layer;
bottom: unset;

Values

<length>

A negative, null, or positive <length>:

for absolutely positioned elements, it represents the distance to the bottom edge of the containing block.
for relatively positioned elements, it represents the distance that the element is moved above its normal position.
for anchor-positioned elements, the anchor() function resolves to a <length> value relative to the position of the associated anchor element's top or bottom edge (see Using inset properties with anchor() function values), and the anchor-size() function resolves to a <length> value relative to the associated anchor element's width or height (see Setting element position based on anchor size).

<percentage>

A <percentage> of the containing block's height.

auto

Specifies that:

for absolutely positioned elements, the position of the element is based on the top property, while height: auto is treated as a height based on the content; or if top is also auto, the element is positioned where it should vertically 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 top property; or if top is also auto, the element is not moved vertically at all.

Description

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

When position is set to absolute or fixed, the bottom property specifies the distance between the outer edge of the element's bottom margin and the outer edge of the containing block's bottom padding, or, in the case of anchor positioned elements when the anchor() function is used within the value, relative to the position of the specified <anchor-side> edge. The bottom property is compatible with the top, bottom, start, end, self-start, self-end, center, and <percentage> values.
When position is set to relative, the bottom property specifies the distance the element's bottom edge is moved above its normal position.
When position is set to sticky, the bottom property is used to compute the sticky-constraint rectangle.
When position is set to static, the bottom property has no effect.

When both top and bottom are specified, position is set to absolute or fixed, and height is unspecified (either auto or 100%) both the top and bottom distances are respected. In all other situations, if height is constrained in any way or position is set to relative, the top property takes precedence and the bottom property is ignored.

Formal definition

Initial value	`auto`
Applies to	positioned elements
Inherited	no
Percentages	refer to the height 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

bottom = 
  auto                 |
  <length-percentage>  |
  <anchor()>           |
  <anchor-size()>      

<length-percentage> = 
  <length>      |
  <percentage>  

<anchor()> = 
  anchor( <anchor-name>?                  &&
  <anchor-side> , <length-percentage>? )  

<anchor-size()> = 
  anchor-size( [ <anchor-name> || <anchor-size> ]? , <length-percentage>? )  

<anchor-name> = 
  <dashed-ident>  

<anchor-side> = 
  inside        |
  outside       |
  top           |
  left          |
  right         |
  bottom        |
  start         |
  end           |
  self-start    |
  self-end      |
  <percentage>  |
  center        

<anchor-size> = 
  width        |
  height       |
  block        |
  inline       |
  self-block   |
  self-inline

Examples

undefined

Absolute and fixed positioning

This example demonstrates the difference in behavior of the bottom property, when position is absolute versus fixed.

HTML

html

<p>
  This<br />is<br />some<br />tall,<br />tall,<br />tall,<br />tall,<br />tall<br />content.
</p>
<div class="fixed"><p>Fixed</p></div>
<div class="absolute"><p>Absolute</p></div>

CSS

css

p {
  font-size: 30px;
  line-height: 2em;
}

div {
  width: 48%;
  text-align: center;
  background: rgb(55 55 55 / 20%);
  border: 1px solid blue;
}

.absolute {
  position: absolute;
  bottom: 0;
  left: 0;
}

.fixed {
  position: fixed;
  bottom: 0;
  right: 0;
}

Result

Specifications

CSS Positioned Layout Module Level 3

bottom CSS property