border-top-width
The border-top-width property is used to set the width of the top border of an element.
The width of the border can be explicitly set using a <length> value, or by using one of three border width keywords: thin, medium, and thick.
Official Syntax
-
Syntax:
border-top-width: <length> | thin | medium | thick
- Initial: medium
- Applies To: all elements
- Animatable: yes
Notes
Note that the initial width is medium, but the initial border style of an element is none and therefore the used width is 0.
Values
- <length>
- The width of the border is set to the specified length. Negative values are not allowed.
- thin
- Implementation-specfic. See note below and the live demo for examples.
- medium
- Implementation-specfic. See note below and the live demo for examples.
- thick
- Implementation-specfic. See note below and the live demo for examples.
Notes
The specification doesn’t precisely define the thickness of each of the keywords, which is therefore implementation specific, but the values are constant throughout a document and thin ? medium ? thick. A browser could, for example, make the thickness depend on the medium font size: one choice might be 1px (for thin), 3px (for medium) & 5px (for thick) when the medium font size is 17px or less.
The border-top-width property can also inherit the value of the element’s parent’s top border width using the keyword inherit.
Examples
The following are all valid border-top-width values set on an element. The element’s border style and border color are also set using the border-top-style and border-top-color respectively.
.element {
border-top-style: dotted;
border-top-color: red;
border-top-width: 10px;
/* or */
border-top-width: thin;
/* or */
border-top-width: 1em;
}
Browser Support
The property works in all major browsers: Chrome, Firefox, Safari, Opera, IE, and on Android and iOS.