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.parentRuleRead only- Returns the containing rule, otherwise
null. E.g. if this rule is a style rule inside an@mediablock, the parent rule would be thatCSSMediaRule. CSSRule.parentStyleSheetRead only- Returns the
CSSStyleSheetobject for the style sheet that contains this rule CSSRule.typeRead 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 | Edge | Firefox (Gecko) | Internet Explorer | Opera | Safari (WebKit) |
|---|---|---|---|---|---|---|
| Basic support | (Yes) | (Yes) | (Yes) | 9 | (Yes) | (Yes) |
CSSKeyframesRule |
? | (Yes) | 20.0 [4] | ? | ? | ? |
CSSCharsetRule |
No support [1] | No support | No support [3] | ? | No support | ? |
CSSUnknownRule |
No support [2] | No support | ? | ? | ? | ? |
| Feature | Android | Android Webview | Edge | Firefox Mobile (Gecko) | IE Phone | Opera Mobile | Safari Mobile | Chrome for Android |
|---|---|---|---|---|---|---|---|---|
| Basic support | ? | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) |
CSSKeyframesRule |
? | ? | (Yes) | 20.0 [4] | ? | ? | ? | ? |
CSSCharsetRule |
? | No support [1] | No support | No support [3] | ? | No support | ? | No support [1] |
CSSUnknownRule |
? | No support [2] | No support | ? | ? | ? | ? | 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.