Custom properties (--*): CSS variables

Baseline Widely available *

This feature is well established and works across many devices and browser versions. It’s been available across browsers since April 2017.

* Some parts of this feature may have varying levels of support.

Property names that are prefixed with --, like --example-name, represent custom properties that contain a value that can be used in other declarations using the var() function.

Custom properties are scoped to the element(s) they are declared on, and participate in the cascade: the value of such a custom property is that from the declaration decided by the cascading algorithm.

Initial valuesee prose
Applies toall elements
Inheritedyes
Computed valueas specified with variables substituted
Animation typediscrete

Syntax

css
--some-keyword: left;
--some-color: #0000ff;
--some-complex-value: 3px 6px rgb(20 32 54);
<declaration-value>

This value matches any sequence of one or more tokens, so long as the sequence does not contain any disallowed token. It represents the entirety of what a valid declaration can have as its value.

Note: Custom property names are case sensitive — --my-color will be treated as a separate custom property to --My-color.

Example

HTML

html
<p id="firstParagraph">
  This paragraph should have a blue background and yellow text.
</p>
<p id="secondParagraph">
  This paragraph should have a yellow background and blue text.
</p>
<div id="container">
  <p id="thirdParagraph">
    This paragraph should have a green background and yellow text.
  </p>
</div>

CSS

css
:root {
  --first-color: #16f;
  --second-color: #ff7;
}

#firstParagraph {
  background-color: var(--first-color);
  color: var(--second-color);
}

#secondParagraph {
  background-color: var(--second-color);
  color: var(--first-color);
}

#container {
  --first-color: #290;
}

#thirdParagraph {
  background-color: var(--first-color);
  color: var(--second-color);
}

Result

Specifications

Specification
CSS Custom Properties for Cascading Variables Module Level 1
# defining-variables

Browser compatibility

Report problems with this compatibility data on GitHub
desktopmobile
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
--*
env()
Safe area inset variable safe-area-inset-bottom
Safe area inset variable safe-area-inset-left
Safe area inset variable safe-area-inset-right
Safe area inset variable safe-area-inset-top
Window Controls Overlay variable titlebar-area-height
Window Controls Overlay variable titlebar-area-width
Window Controls Overlay variable titlebar-area-x
Window Controls Overlay variable titlebar-area-y
var()

Legend

Tip: you can click/tap on a cell for more information.

Full support
Full support
Partial support
Partial support
No support
No support
Uses a non-standard name.
Has more compatibility info.

See also