border-bottom-width

CSS 属性 border-bottom-width 设置一个元素的底部边框宽度。

/* Keyword values */
border-bottom-width: thin;
border-bottom-width: medium;
border-bottom-width: thick;

/* <length> values */
border-bottom-width: 10em;
border-bottom-width: 3vmax;
border-bottom-width: 6px;

/* Global keywords */
border-bottom-width: inherit;
border-bottom-width: initial;
border-bottom-width: unset;

初始值	`medium`
适用元素	all elements. It also applies to `::first-letter`.
是否是继承属性	否
计算值	the absolute length or `0` if `border-bottom-style` is `none` or `hidden`
Animation type	a length

Syntax

Values

<br-width>

定义边框宽度，取值为非负的宽度值<length>或关键字。如果是关键字的话，其取值必须是以下之一：

`thin`		细边框
`medium`		中等边框
`thick`		粗边框

Note: 因为规范没有具体定义每个关键字对应的宽度值，所以实际显示效果依赖于实现。但是宽度值的取值一定遵循 thin ≤ medium ≤ thick 的规律且在单文档中是常数。

Formal syntax

<line-width>where 
<line-width> = <length> | thin | medium | thick

Example

HTML

<div>Element 1</div>
<div>Element 2</div>

CSS

div { 
  border: 1px solid red;
  margin: 1em 0;
}

div:nth-child(1) {
  border-bottom-width: thick;
}
div:nth-child(2) {
  border-bottom-width: 2em;
}

Result

Specifications

Specification	Status	Comment
CSS Backgrounds and Borders Module Level 3 border-bottom-width	Candidate Recommendation	No significant change.
CSS Level 2 (Revision 1) border-bottom-width	Recommendation	No significant change.
CSS Level 1 border-bottom-width	Recommendation	Initial definition.

Browser compatibility

Update compatibility data on GitHub

	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
`border-bottom-width`	Chrome Full support 1	Edge Full support 12	Firefox Full support 1	IE Full support 4	Opera Full support 3.5	Safari Full support 1	WebView Android Full support 2.3	Chrome Android Full support 18	Firefox Android Full support 4	Opera Android Full support 10.1	Safari iOS Full support 1	Samsung Internet Android Full support 1.0

Legend

Full support: Full support