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border-left-width

The border-left-width CSS property sets the width of the left border of an element.

Syntax

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

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

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

Values

<line-width>
Defines the width of the border, either as an explicit nonnegative <length> or a keyword. If it's a keyword, it must be one of the following values:
thin A thin border
medium A medium border
thick A thick border

Note: Because the specification doesn't define the exact thickness denoted by each keyword, the precise result when using one of them is implementation-specific. Nevertheless, they always follow the pattern thin ≤ medium ≤ thick, and the values are constant within a single document.

Formal definition

Initial value medium
Applies to all elements. It also applies to ::first-letter.
Inherited no
Computed value the absolute length or 0 if border-left-style is none or hidden
Animation type a length

Formal syntax

<line-width>

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

Examples

Comparing border widths

HTML

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

CSS

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

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

Result

Specifications

Browser compatibilityUpdate compatibility data on GitHub

Desktop
Chrome Edge Firefox Internet Explorer Opera Safari
border-left-width 1 12 1 4 3.5 1
Mobile
Android webview Chrome for Android Firefox for Android Opera for Android Safari on iOS Samsung Internet
border-left-width 2.3 18 4 10.1 1 1.0

See also

© 2005–2020 Mozilla and individual contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/CSS/border-left-width