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
:root { --main-bg-color: pink; } body { background-color: var(--main-bg-color); }
/* 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 1 The definition of 'var()' in that specification. |
Candidate Recommendation | Initial definition |
Browser compatibility
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
var() | Chrome
Full support
49
| Edge Full support 15 | Firefox
Full support
31
| IE No support No | Opera Full support 36 | Safari Full support 9.1 | WebView Android Full support 50 | Chrome Android
Full support
49
| Firefox Android
Full support
31
| 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.
See also
env(…)
– read‑only environment variables controlled by the user‑agent.- Using CSS variables