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.

Browser compatibility

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.

See also

Document Tags and Contributors

 Last updated by: Nickolay,