CSS Properties and Values API

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 CSS Properties and Values API — part of the CSS Houdini umbrella of APIs — allows developers to explicitly define their CSS custom properties, allowing for property type checking, default values, and properties that do or do not inherit their value.

Interfaces

CSS.registerProperty

Defines how a browser should parse CSS custom properties. Access this interface through CSS.registerProperty in JavaScript.

@property

Defines how a browser should parse CSS custom properties. Access this interface through @property at-rule in CSS.

Examples

The following will register a custom property named --my-color using CSS.registerProperty in JavaScript. --my-color will use the CSS color syntax, it will have a default value of #c0ffee, and it will not inherit its value:

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

The same registration can take place in CSS using the @property at-rule:

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

Specifications

Specification
CSS Properties and Values API Level 1
# the-css-property-rule-interface
CSS Properties and Values API Level 1
# the-registerproperty-function

Browser compatibility

api.CSSPropertyRule

desktop mobile
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
CSSPropertyRule
Chrome – Full support
Chrome 85 (Release date: 2020-08-25)
footnote Full support
Edge – Full support
Edge 85 (Release date: 2020-08-27)
footnote Full support
Firefox – Full support
Firefox 128 (Release date: 2024-07-09)
footnote Full support
Opera – Full support
Opera 71 (Release date: 2020-09-15)
footnote Full support
Safari – Full support
Safari 16.4 (Release date: 2023-03-27)
footnote Full support
Chrome Android – Full support
Chrome Android 85 (Release date: 2020-08-25)
footnote Full support
Firefox for Android – Full support
Firefox for Android 128 (Release date: 2024-07-09)
footnote Full support
Opera Android – Full support
Opera Android 60 (Release date: 2020-09-23)
footnote Full support
Safari on iOS – Full support
Safari on iOS 16.4 (Release date: 2023-03-27)
footnote Full support
Samsung Internet – Full support
Samsung Internet 14 (Release date: 2021-04-17)
footnote Full support
WebView Android – Full support
WebView Android 85 (Release date: 2020-08-25)
footnote Full support
WebView on iOS – Full support
WebView on iOS 16.4 (Release date: 2023-03-27)
footnote Full support
inherits
Chrome – Full support
Chrome 85 (Release date: 2020-08-25)
footnote Full support
Edge – Full support
Edge 85 (Release date: 2020-08-27)
footnote Full support
Firefox – Full support
Firefox 128 (Release date: 2024-07-09)
footnote Full support
Opera – Full support
Opera 71 (Release date: 2020-09-15)
footnote Full support
Safari – Full support
Safari 16.4 (Release date: 2023-03-27)
footnote Full support
Chrome Android – Full support
Chrome Android 85 (Release date: 2020-08-25)
footnote Full support
Firefox for Android – Full support
Firefox for Android 128 (Release date: 2024-07-09)
footnote Full support
Opera Android – Full support
Opera Android 60 (Release date: 2020-09-23)
footnote Full support
Safari on iOS – Full support
Safari on iOS 16.4 (Release date: 2023-03-27)
footnote Full support
Samsung Internet – Full support
Samsung Internet 14 (Release date: 2021-04-17)
footnote Full support
WebView Android – Full support
WebView Android 85 (Release date: 2020-08-25)
footnote Full support
WebView on iOS – Full support
WebView on iOS 16.4 (Release date: 2023-03-27)
footnote Full support
initialValue
Chrome – Full support
Chrome 85 (Release date: 2020-08-25)
footnote Full support
Edge – Full support
Edge 85 (Release date: 2020-08-27)
footnote Full support
Firefox – Full support
Firefox 128 (Release date: 2024-07-09)
footnote Full support
Opera – Full support
Opera 71 (Release date: 2020-09-15)
footnote Full support
Safari – Full support
Safari 16.4 (Release date: 2023-03-27)
footnote Full support
Chrome Android – Full support
Chrome Android 85 (Release date: 2020-08-25)
footnote Full support
Firefox for Android – Full support
Firefox for Android 128 (Release date: 2024-07-09)
footnote Full support
Opera Android – Full support
Opera Android 60 (Release date: 2020-09-23)
footnote Full support
Safari on iOS – Full support
Safari on iOS 16.4 (Release date: 2023-03-27)
footnote Full support
Samsung Internet – Full support
Samsung Internet 14 (Release date: 2021-04-17)
footnote Full support
WebView Android – Full support
WebView Android 85 (Release date: 2020-08-25)
footnote Full support
WebView on iOS – Full support
WebView on iOS 16.4 (Release date: 2023-03-27)
footnote Full support
name
Chrome – Full support
Chrome 85 (Release date: 2020-08-25)
footnote Full support
Edge – Full support
Edge 85 (Release date: 2020-08-27)
footnote Full support
Firefox – Full support
Firefox 128 (Release date: 2024-07-09)
footnote Full support
Opera – Full support
Opera 71 (Release date: 2020-09-15)
footnote Full support
Safari – Full support
Safari 16.4 (Release date: 2023-03-27)
footnote Full support
Chrome Android – Full support
Chrome Android 85 (Release date: 2020-08-25)
footnote Full support
Firefox for Android – Full support
Firefox for Android 128 (Release date: 2024-07-09)
footnote Full support
Opera Android – Full support
Opera Android 60 (Release date: 2020-09-23)
footnote Full support
Safari on iOS – Full support
Safari on iOS 16.4 (Release date: 2023-03-27)
footnote Full support
Samsung Internet – Full support
Samsung Internet 14 (Release date: 2021-04-17)
footnote Full support
WebView Android – Full support
WebView Android 85 (Release date: 2020-08-25)
footnote Full support
WebView on iOS – Full support
WebView on iOS 16.4 (Release date: 2023-03-27)
footnote Full support
syntax
Chrome – Full support
Chrome 85 (Release date: 2020-08-25)
footnote Full support
Edge – Full support
Edge 85 (Release date: 2020-08-27)
footnote Full support
Firefox – Full support
Firefox 128 (Release date: 2024-07-09)
footnote Full support
Opera – Full support
Opera 71 (Release date: 2020-09-15)
footnote Full support
Safari – Full support
Safari 16.4 (Release date: 2023-03-27)
footnote Full support
Chrome Android – Full support
Chrome Android 85 (Release date: 2020-08-25)
footnote Full support
Firefox for Android – Full support
Firefox for Android 128 (Release date: 2024-07-09)
footnote Full support
Opera Android – Full support
Opera Android 60 (Release date: 2020-09-23)
footnote Full support
Safari on iOS – Full support
Safari on iOS 16.4 (Release date: 2023-03-27)
footnote Full support
Samsung Internet – Full support
Samsung Internet 14 (Release date: 2021-04-17)
footnote Full support
WebView Android – Full support
WebView Android 85 (Release date: 2020-08-25)
footnote Full support
WebView on iOS – Full support
WebView on iOS 16.4 (Release date: 2023-03-27)
footnote Full support

Legend

Tip: you can click/tap on a cell for more information.

Full support
Full support

api.CSS.registerProperty_static

desktop mobile
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
registerProperty() static method
Chrome – Full support
Chrome 78 (Release date: 2019-10-22)
footnote Full support
Edge – Full support
Edge 79 (Release date: 2020-01-15)
footnote Full support
Firefox – Full support
Firefox 128 (Release date: 2024-07-09)
footnote Full support
Opera – Full support
Opera 65 (Release date: 2019-11-13)
footnote Full support
Safari – Full support
Safari 16.4 (Release date: 2023-03-27)
footnote Full support
Chrome Android – Full support
Chrome Android 78 (Release date: 2019-10-22)
footnote Full support
Firefox for Android – Full support
Firefox for Android 128 (Release date: 2024-07-09)
footnote Full support
Opera Android – Full support
Opera Android 56 (Release date: 2020-02-06)
footnote Full support
Safari on iOS – Full support
Safari on iOS 16.4 (Release date: 2023-03-27)
footnote Full support
Samsung Internet – Full support
Samsung Internet 12 (Release date: 2020-06-19)
footnote Full support
WebView Android – Full support
WebView Android 78 (Release date: 2019-10-22)
footnote Full support
WebView on iOS – Full support
WebView on iOS 16.4 (Release date: 2023-03-27)
footnote Full support

Legend

Tip: you can click/tap on a cell for more information.

Full support
Full support

See also