The border-top-width CSS property sets the width of the top border of a box.
/* Any <length> value */ border-top-width: 10em; border-top-width: 3vmax; border-top-width: 6px; /* A keyword */ border-top-width: thin; border-top-width: medium; border-top-width: thick; border-top-width: inherit;
| Initial value | medium | 
|---|---|
| Applies to | all elements. It also applies to ::first-letter. | 
| Inherited | no | 
| Media | visual | 
| Computed value | the absolute length or 0ifborder-top-styleisnoneorhidden | 
| Animation type | a length | 
| Canonical order | the unique non-ambiguous order defined by the formal grammar | 
Syntax
Values
- <br-width>
- Is either a non-negative explicit <length>value or a keyword denoting the thickness of the bottom border. The keyword must be one of the following values:
 The specification doesn't precisely define the thickness of each of the keywords, which is therefore implementation specific. Nevertheless, it requests that the thickness does follow thethinA thin border mediumA medium border thickA thick border thin ≤ medium ≤ thickinequality and that the values are constant on a single document.
- inherit
- Represents the calculated value of the border-top-widthof the parent's element.
Formal syntax
<br-width>
Examples
element { 
    border-top-width: thin;
    border-top-style: solid;
    border-top-color: #000;
}
.element1{
	border-top: thick solid red;
}
.element2{
	border-top: medium solid orange;
}
.element3{
	border-top: thin solid green;
}
Live Sample
Element 1
Element 2
Element 3
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 | Initial definition | 
Browser compatibility
| Feature | Chrome | Edge | Firefox (Gecko) | Internet Explorer | Opera | Safari (WebKit) | 
|---|---|---|---|---|---|---|
| Basic support | 1.0 | (Yes) | 1.0 (1.0) | 4.0 | 3.5 | 1.0 (85) | 
| Feature | Android | Edge | Firefox Mobile (Gecko) | IE Phone | Opera Mobile | Safari Mobile | 
|---|---|---|---|---|---|---|
| Basic support | ? | (Yes) | ? | ? | ? | ? | 
See also
- The other border-width-related CSS properties: border-left-width,border-right-width,border-bottom-width, andborder-width
- The other border-top-related CSS properties: border,border-top,border-top-style, andborder-top-color.
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