border-left-width property CSS Reference

Definition and Usage

The border-left-width CSS property sets the width of the left border of a box.

  • Initial medium
  • Applies to all elements
  • Inherited no
  • Media visual
  • Computed Value the absolute length or 0 if border-left-style is none or hidden
  • Animatable yes, as a length
  • Canonical order the unique non-ambiguous order defined by the formal grammar


Formal syntax: <br-width>
border-left-width: 10em    /* Any <length> value */
border-left-width: 3vmax
border-left-width: 6px
border-left-width: thin    /* A keyword */
border-left-width: medium
border-left-width: thick
border-left-width: inherit


Is either a non-negative explicit <length> value or a keyword denoting the thickness of the left border. The keyword must be one of the following values:
Style Preview Description
A thin border
A medium border
A thick border
The specification doesn't define precisely the thickness of each fo the keywords, which is therefore implementation specific. Nevertheless, it requests that the thickness does follow the thin ≤ medium ≤ thick pattern and is constant on a single document.
Represents the calculated value of the border-left-width of the parent's element.


element {
  border-left-width: thin;
  border-left-style: solid;
  border-left-color: #000;


Desktop browsers

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 1.0 1.0 (1.0) 4.0 3.5 1.0 (85)

Mobile browsers

Feature Android Firefox Mobile (Gecko) IE Phone Opera Mobile Safari Mobile
Basic support NA NA NA NA NA

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