CSSKeyframesRule

Animations (CSS) animations-css

Baseline: Widely available on the web, in every major browser since Sep 2015, and long enough to count on (since Mar 2018).

niso: Partial 56%. 649 of 1148 subtests pass, by system: Linux 56%, macOS 56%. Engines: QuickJS, the engine niso's WPT run uses; Node and Porffor have no recorded run. WPT results recorded at f3b4fa8, 2026-11-10; web-features 3.45.0. WPT tests · niso's support · CSSKeyframeRule, CSSKeyframesRule

CSSKeyframesRule is an interface in idl/cssom.webidl, inheriting CSSRule, exposed in Window. What it does is on MDN; this page says what niso has of it.

Status

The web features its members belong to, each with its Baseline status on the web and how much of the feature’s WPT suite passes in niso (see Web platform support).

Feature	On the web	In niso	Members
Animations (CSS)	Widely available	Partial 56% 649 of 1148 subtests pass	5

Members

name

attribute

readonly attribute DOMString name;

int32_t niso_css_keyframes_rule_get_name(niso_dom* dom, niso_handle self, niso_str* out);

cssRules

attribute

readonly attribute CSSRuleList cssRules;

int32_t niso_css_keyframes_rule_get_css_rules(niso_dom* dom, niso_handle self, niso_handle* out);

length

attribute

readonly attribute unsigned long length;

int32_t niso_css_keyframes_rule_get_length(niso_dom* dom, niso_handle self, uint32_t* out);

item()

operation

getter CSSKeyframeRule? item(unsigned long index);

int32_t niso_css_keyframes_rule_item(niso_dom* dom, niso_handle self, uint32_t index, niso_handle* out);

appendRule()

operation

undefined appendRule(DOMString rule);

int32_t niso_css_keyframes_rule_append_rule(niso_dom* dom, niso_handle self, const char* rule, size_t rule_len);

Not in niso yet

Members the web has, by the BCD keys web-features 3.45.0 lists, that idl/ doesn’t declare. The list is partial: web-features lists only the keys it maps to a feature.

• deleteRule (Animations (CSS))
• findRule (Animations (CSS))