initial-value

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

Syntax

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

/* Set initial length value */
initial-value: 16px;

Values

A value that matches the type specified in the {{cssxref("@property/syntax", "syntax")}} descriptor. For example, if syntax is <color>, then the initial-value must be a valid {{cssxref("color")}} value.

If the value of the syntax descriptor is not the universal syntax definition, the initial-value descriptor has to be a computationally independent value. This means the value can be converted into a computed value without depending on other values, except for “global” definitions independent of CSS. For example, 10px is computationally independent—it doesn’t change when converted to a computed value. 2in is also valid, because 1in is always equivalent to 96px. However, 3em is not valid, because the value of an em is dependent on the parent’s {{cssxref("font-size")}} .

Formal definition

{{cssinfo}}

Formal syntax

{{csssyntax}}

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.

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

Using JavaScript {{domxref('CSS.registerProperty_static', 'CSS.registerProperty()')}} :

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

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

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