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/CSS

border-top-width

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

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

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

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

Initial value	`medium`
Applies to	all elements. It also applies to `::first-letter`.
Inherited	no
Media	visual
Computed value	the absolute length or `0` if `border-top-style` is `none` or `hidden`
Animation type	a length
Canonical order	the unique non-ambiguous order defined by the formal grammar

Syntax

Values

<br-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 syntax

<br-width>where 
<br-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-top-width: thick;
}
div:nth-child(2) {
  border-top-width: 2em;
}

Result

Specifications

Specification	Status	Comment
CSS Backgrounds and Borders Module Level 3 The definition of 'border-top-width' in that specification.	Candidate Recommendation	No significant change.
CSS Level 2 (Revision 1) The definition of 'border-top-width' in that specification.	Recommendation	No significant change.
CSS Level 1 The definition of 'border-top-width' 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	2.3	?	Yes	4	6	11	1