Web/CSS/var()

The var() CSS function can be used to insert the value of a custom property (sometimes called a "CSS variable") instead of any part of a value of another property.

The var() function cannot be used in property names, selectors or anything else besides property values. (Doing so usually produces invalid syntax, or else a value whose meaning has no connection to the variable.)

Syntax

The first argument to the function is the name of the custom property to be substituted. An optional second argument to the function serves as a fallback value. If the custom property referenced by the first argument is invalid, the function uses the second value.

var( <custom-property-name> , <declaration-value>? )

Note: The syntax of the fallback, like that of custom properties, allows commas. For example, var(--foo, red, blue) defines a fallback of red, blue; that is, anything between the first comma and the end of the function is considered a fallback value.

Values

<custom-property-name>: A custom property’s name represented by an identifier that starts with two dashes. Custom properties are solely for use by authors and users; CSS will never give them a meaning beyond what is presented here.
<declaration-value>: The custom property's fallback value, which is used in case the custom property is invalid in the used context. This value may contain any character except some characters with special meaning like newlines, unmatched closing brackets, i.e. ), ], or }, top-level semicolons, or exclamation marks.

Examples

Using a custom property set on :root

:root {
  --main-bg-color: pink;
}

body {
  background-color: var(--main-bg-color);
}

Custom properties with fallbacks for use when the property has not been set

/* Fallback */
/* In the component’s style: */
.component .header {
  color: var(--header-color, blue); /* header-color isn’t set, and so remains blue, the fallback value */
}

.component .text {
  color: var(--text-color, black);
}

/* In the larger application’s style: */
.component {
  --text-color: #080;
}

Specifications

Specification	Status	Comment
CSS Custom Properties for Cascading Variables Module Level 1The definition of 'var()' in that specification.	Candidate Recommendation	Initial definition

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`var()`	Chrome Full support 49 Full support 49 Full support 48 Disabled' Disabled' From version 48: this feature is behind the `Enable experimental Web Platform features` preference. To change preferences in Chrome, visit chrome://flags.	Edge Full support 15	Firefox Full support 31 Full support 31 No support 29 — 55 Disabled' Disabled' From version 29 until version 55 (exclusive): this feature is behind the `layout.css.variables.enabled` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	IE No support No	Opera Full support 36	Safari Full support 9.1	WebView Android Full support 50	Chrome Android Full support 49 Full support 49 Full support 48 Disabled' Disabled' From version 48: this feature is behind the `Enable experimental Web Platform features` preference. To change preferences in Chrome, visit chrome://flags.	Firefox Android Full support 31 Full support 31 No support 29 — 55 Disabled' Disabled' From version 29 until version 55 (exclusive): this feature is behind the `layout.css.variables.enabled` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	Opera Android Full support 36	Safari iOS Full support 9.3	Samsung Internet Android Full support 5.0

Legend

Full support: Full support
No support: No support
User must explicitly enable this feature.': User must explicitly enable this feature.