initial-value

Baseline 2024
Newly available

Since July 2024, this feature works across the latest devices and browser versions. This feature might not work in older devices or browsers.

The initial-value descriptor of the @property at-rule specifies the initial value for the registered CSS custom property. It is a required descriptor unless the syntax descriptor value is the universal syntax (*). If required but missing or invalid, the entire @property rule is invalid and ignored.

Syntax

css
/* Set initial color value */
initial-value: rebeccapurple;

/* Set initial length value */
initial-value: 2rem;

Values

A value that matches the type specified in the syntax descriptor. For example, if syntax is <color>, then the initial-value must be a valid color value.

Formal definition

Related at-rule@property
Initial valuen/a (required)
Computed valueas specified

Formal syntax

initial-value = 
<declaration-value>?

Examples

Setting an initial value for a custom property

This example shows how to define a custom property --my-color with an initial color value of #c0ffee. This initial value will be used when the property is not inherited (inherits: false) and no other value is set on the element.

css
@property --my-color {
  syntax: "<color>";
  inherits: false;
  initial-value: #c0ffee;
}

Using JavaScript CSS.registerProperty():

js
window.CSS.registerProperty({
  name: "--my-color",
  syntax: "<color>",
  inherits: false,
  initialValue: "#c0ffee",
});

Specifications

Specification
CSS Properties and Values API Level 1
# initial-value-descriptor

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
initial-value descriptor

Legend

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Full support
Full support

See also