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border-bottom

The border-bottom CSS property is a shorthand that sets the values of border-bottom-color, border-bottom-style, and border-bottom-width. These properties describe an element's bottom border.

border-bottom: 1px;
border-bottom: 2px dotted;
border-bottom: medium dashed blue;

As with all shorthand properties, border-bottom always sets the values of all of the properties that it can set, even if they are not specified. It sets those that are not specified to their default values. This means that ...

border-bottom-style: dotted;
border-bottom: thick green;
... is actually the same as ...
border-bottom-style: dotted;
border-bottom: none thick green;

... and the value of border-bottom-style given before border-bottom is ignored. Since the default value of border-bottom-style is none, not specifying the border-style part results in no border.

Initial value as each of the properties of the shorthand:
Applies to all elements. It also applies to ::first-letter.
Inherited no
Media visual
Computed value as each of the properties of the shorthand:
Animation type as each of the properties of the shorthand:
Canonical order order of appearance in the formal grammar of the values

Syntax

The three values of the shorthand property can be specified in any order, and one or two of them may be omitted.

Values

<br-width> 
See border-bottom-width.
<br-style> 
See border-bottom-style.
<color>
See border-bottom-color.

Formal syntax

<br-width> || <br-style> || <color>

where
<br-width> = <length> | thin | medium | thick
<br-style> = none | hidden | dotted | dashed | solid | double | groove | ridge | inset | outset
<color> = <rgb()> | <rgba()> | <hsl()> | <hsla()> | <hex-color> | <named-color> | currentcolor | <deprecated-system-color>

where
<rgb()> = rgb( [ [ <percentage>{3} | <number>{3} ] [ / <alpha-value> ]? ] | [ [ <percentage>#{3} | <number>#{3} ] , <alpha-value>? ] )
<rgba()> = rgba( [ [ <percentage>{3} | <number>{3} ] [ / <alpha-value> ]? ] | [ [ <percentage>#{3} | <number>#{3} ] , <alpha-value>? ] )
<hsl()> = hsl( [ <hue> <percentage> <percentage> [ / <alpha-value> ]? ] | [ <hue>, <percentage>, <percentage>, <alpha-value>? ] )
<hsla()> = hsla( [ <hue> <percentage> <percentage> [ / <alpha-value> ]? ] | [ <hue>, <percentage>, <percentage>, <alpha-value>? ] )

where
<alpha-value> = <number> | <percentage>
<hue> = <number> | <angle>

Example

<div>
  This box has a border on the bottom side.
</div>
div {
  border-bottom: 4px dashed blue;
  background-color: gold;
  height: 100px;
  width: 100px;
  font-weight: bold;
  text-align: center;
}

Specifications

Specification Status Comment
CSS Backgrounds and Borders Module Level 3
The definition of 'border-bottom' in that specification.
Candidate Recommendation No direct changes, though the modification of values for the border-bottom-color do apply to it.
CSS Level 2 (Revision 1)
The definition of 'border-bottom' in that specification.
Recommendation No significant changes.
CSS Level 1
The definition of 'border-bottom' in that specification.
Recommendation Initial definition.

Browser compatibility

Feature Chrome Edge Firefox Internet Explorer Opera Safari
Basic support 1 Yes 1 4 3.5 1
Feature Android webview Chrome for Android Edge mobile Firefox for Android IE mobile Opera Android iOS Safari
Basic support 1 ? Yes 4 Yes Yes Yes

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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/CSS/border-bottom