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initial-value

The initial-value CSS descriptor is required when using the @property at-rule unless the syntax accepts any valid token stream. It sets the initial-value for the property.

The value chosen as the initial-value must parse correctly according to the syntax definition. Therefore, if syntax is <color> then the initial-value must be a valid color value.

Syntax

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

@property --property-name {
  syntax: "<color>";
  inherits: true;
  initial-value: #c0ffee;
}

Values

A string with a value which is a correct value for the chosen syntax.

Formal definition

Related at-rule	`@property`
Initial value	`n/a (required)`
Computed value	as specified

Formal syntax

initial-value = 
  <declaration-value>

Examples

Add type checking to --my-color custom property, as a color, the initial-value being a valid color:

Using CSS @property at-rule:

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

Using JavaScript CSS.registerProperty:

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

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	WebView Android	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet
`initial-value`	85	85	No	No	71	16.4	85	85	No	60	16.4	14.0