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The border-bottom-left-radius CSS property sets the rounding of the bottom-left corner of the element. The rounding can be a circle or an ellipse, or if one of the value is 0 no rounding is done and the corner is square.

border-bottom-left-radius CSS 设置元素左下角的圆形样式. 这个圆形可以是图的或椭圆, 当值为0时就为普通的直角边角.


背景不管是图片还是颜色,都会被这个属性影响其形状; 关于此,准确的属性设置在 background-clip 属性.

假如 border-radius 简写属性出现在 border-bottom-left-radius CSS 属性后边, 其值会被这个简写重置 shorthand property.

适用元素all elements; but User Agents are not required to apply to table and inline-table elements when border-collapse is collapse. The behavior on internal table elements is undefined for the moment.. It also applies to ::first-letter.
Percentagesrefer to the corresponding dimension of the border box
计算值two absolute lengths or percentages
Animation typea length, percentage or calc();
正规顺序the unique non-ambiguous order defined by the formal grammar


/* 圆形 */
/* border-bottom-left-radius: radius */
border-bottom-left-radius: 3px;

/* 椭圆形 */
/* border-bottom-left-radius: 水平方向 垂直方向 */
border-bottom-left-radius: 0.5em 1em;

border-bottom-left-radius: inherit;


Is a <length> or a <percentage> denoting the radius of the circle to use for the border in that corner.
Is a <length> or a <percentage> denoting the horizontal semi-major axis of the ellipsis to use for the border in that corner.
Is a <length> or a <percentage> denoting the vertical semi-major axis of the ellipsis to use for the border in that corner.


Denotes the size of the circle radius or the semi-major and semi-minor axes of the ellipsis. As absolute length it can be expressed in any unit allowed by the CSS <length> data type. Percentages for the horizontal axis refer to the width of the box, percentages for the vertical axis refer to the height of the box. Negative values are invalid.

Formal syntax


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


Live example Code
An arc of circle is used as the border
div {
  border-bottom-left-radius: 40px 40px;
An arc of ellipse is used as the border
div {
  border-bottom-left-radius: 40px 20px;
The box is a square: an arc of circle is used as the border
div {
  border-bottom-left-radius: 40%;
The box is not a square: an arc of ellipse is used as the border
div {
  border-bottom-left-radius: 40%;
The background color is clipped at the border
div {
  border-style: black 3px double;
  background-color: rgb(250,20,70);
  background-clip: content-box;


Specification Status Comment
CSS Backgrounds and Borders Module Level 3
Candidate Recommendation Initial definition

Browser compatibility

We're converting our compatibility data into a machine-readable JSON format. This compatibility table still uses the old format, because we haven't yet converted the data it contains. Find out how you can help!

Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 1.0 -webkit
1.0 (1.0)-moz[1]
4.0 (2.0)[3]
9.0 10.5 3.0 (522)-webkit
5.0 (532.5)
Percentages 4.0 ? 1.0 (1.0)[2]
4.0 (2.0)
9.0 10.5 5.0 (532.5)
Elliptical corners 1.0 ? 3.5 (1.9.1) 9.0 10.5 3.0 (522)
Feature Android Edge Firefox Mobile (Gecko) IE Phone Opera Mobile Safari Mobile
Basic support ? (Yes)-webkit
(Yes)[3] ? ? ?
Percentages ? ? (Yes) ? ? ?
Elliptical corners ? ? (Yes) ? ? ?

[1] The prefixed version (allowed from Firefox 1 to Firefox 12) of this property uses a different name, -moz-border-radius-bottomleft, than the final property as Mozilla implemented it before the final name was coined.

[2] Before Firefox 4, the <percentage> was relative to the width of the box even when specifying the radius for a height). This implied that -moz-border-radius-bottomleft was always drawing an arc of circle, and never an ellipse, when followed by a single value.

[3] Prior to Gecko 50.0 (Firefox 50.0 / Thunderbird 50.0 / SeaMonkey 2.47), border styles of rounded corners were always rendered as if border-style was solid. This has been fixed in Gecko 50.0.

In addition to the unprefixed support, Gecko 44.0 (Firefox 44.0 / Thunderbird 44.0 / SeaMonkey 2.41) added support for a -webkit prefixed version of the property for web compatibility reasons behind the preference layout.css.prefixes.webkit, defaulting to false. Since Gecko 49.0 (Firefox 49.0 / Thunderbird 49.0 / SeaMonkey 2.46) the preference defaults to true.

See also

The border-radius-related CSS properties: the CSS shorthand border-radius, the properties for the other corners: border-top-right-radius, border-bottom-right-radius, and border-top-left-radius.