CSSRule

The CSSRule interface represents a single CSS rule. There are several types of rules, listed in the Type constants section below.

The CSSRule interface specifies the properties common to all rules, while properties unique to specific rule types are specified in the more specialized interfaces for those rules' respective types.

References to a CSSRule may be obtained by looking at a CSSStyleSheet's cssRules list.

Properties common to all CSSRule instances

CSSRule.cssText: Represents the textual representation of the rule, e.g. "h1,h2 { font-size: 16pt }" or "@import 'url'". To access or modify parts of the rule (e.g. the value of "font-size" in the example) use the properties on the specialized interface for the rule's type.
CSSRule.parentRule Read only: Returns the containing rule, otherwise null. E.g. if this rule is a style rule inside an @media block, the parent rule would be that CSSMediaRule.
CSSRule.parentStyleSheet Read only: Returns the CSSStyleSheet object for the style sheet that contains this rule
CSSRule.type Read only: One of the Type constants indicating the type of CSS rule.

Constants

Type constants

The CSSRule interface specifies integer constants that can be used in conjunction with a CSSRule's type property to discern the rule type (and therefore, which specialized interface it implements). The relationships between these constants and the interfaces are:

Type	Value	Rule-specific interface	Comments and examples
`CSSRule.STYLE_RULE`	`1`	`CSSStyleRule`	The most common kind of rule: `selector { prop1: val1; prop2: val2; }`
`CSSRule.IMPORT_RULE`	`3`	`CSSImportRule`	An `@import` rule. (Until the documentation is completed, see the interface definition in the Mozilla source code: nsIDOMCSSImportRule.)
`CSSRule.MEDIA_RULE`	`4`	`CSSMediaRule`
`CSSRule.FONT_FACE_RULE`	`5`	`CSSFontFaceRule`
`CSSRule.PAGE_RULE`	`6`	`CSSPageRule`
`CSSRule.KEYFRAMES_RULE`	`7`	`CSSKeyframesRule`
`CSSRule.KEYFRAME_RULE`	`8`	`CSSKeyframeRule`
Reserved for future use	`9`		Should be used to define color profiles in the future
`CSSRule.NAMESPACE_RULE`	`10`	`CSSNamespaceRule`
`CSSRule.COUNTER_STYLE_RULE`	`11`	`CSSCounterStyleRule`
`CSSRule.SUPPORTS_RULE`	`12`	`CSSSupportsRule`
`CSSRule.DOCUMENT_RULE`	`13`	`CSSDocumentRule`
`CSSRule.FONT_FEATURE_VALUES_RULE`	`14`	`CSSFontFeatureValuesRule`
`CSSRule.VIEWPORT_RULE`	`15`	`CSSViewportRule`
`CSSRule.REGION_STYLE_RULE`	`16`	`CSSRegionStyleRule`
`CSSRule.UNKNOWN_RULE`	`0`	`CSSUnknownRule`
`CSSRule.CHARSET_RULE`	`2`	`CSSCharsetRule`	(Removed in most browsers.)

An up-to-date informal list of constants can be found on the CSSWG Wiki.

Specifications

Specification	Status	Comment
CSS Object Model (CSSOM) The definition of 'CSSRule' in that specification.	Working Draft	Obsoleted values `CHARSET_RULE` and `UNKNOWN_RULE`. Added value `NAMESPACE_RULE`.
CSS Animations The definition of 'CSSRule' in that specification.	Working Draft	Added values `KEYFRAMES_RULE` and `KEYFRAME_RULE`.
CSS Fonts Module Level 3 The definition of 'CSSRule' in that specification.	Candidate Recommendation	Added value `FONT_FEATURE_VALUES_RULE`.
CSS Counter Styles Level 3 The definition of 'CSSRule' in that specification.	Candidate Recommendation	Added value `COUNTER_STYLE_RULE`.
CSS Conditional Rules Module Level 3 The definition of 'CSSRule' in that specification.	Candidate Recommendation	Added value `SUPPORTS_RULE`. (`DOCUMENT_RULE` has been pushed to CSS Conditional Rules Level 4)
Document Object Model (DOM) Level 2 Style Specification The definition of 'CSSRule' in that specification.	Recommendation	Initial definition.

Feature	Chrome	Firefox (Gecko)	Internet Explorer	Opera	Safari (WebKit)
Basic support	(Yes)	(Yes)	9	(Yes)	(Yes)
`CSSKeyframesRule`	?	20.0 [4]	?	?	?
`CSSCharsetRule`	No support [1]	No support [3]	?	No support	?
`CSSUnknownRule`	No support [2]	?	?	?	?

Feature	Android	Android Webview	Firefox Mobile (Gecko)	IE Phone	Opera Mobile	Safari Mobile	Chrome for Android
Basic support	?	(Yes)	(Yes)	(Yes)	(Yes)	(Yes)	(Yes)
`CSSKeyframesRule`	?	?	20.0 [4]	?	?	?	?
`CSSCharsetRule`	?	No support [1]	No support [3]	?	No support	?	No support [1]
`CSSUnknownRule`	?	No support [2]	?	?	?	?	No support [2]

[1] CSSCharsetRule was removed in Chrome version 41.0.

[2] CSSUnknownRule was removed in Chrome version 45.0.

[3] CSSCharsetRule was removed in Gecko version 40.

[4] On Gecko, before Firefox 19, the keyframe-related constants existed only in their prefixed version: CSSRule.MOZ_KEYFRAMES_RULE and CSSRule.MOZ_KEYFRAME_RULE. From Firefox 20 onwards, both versions are available. The prefixed version will be removed in the future.