CSSContainerRule

Container queries (size) container-queries

Baseline: Widely available on the web, in every major browser since Feb 2023, and long enough to count on (since Aug 2025).

niso: Partial 0.3%. 3 of 830 subtests pass, by system: Linux 0.3%, macOS 0.3%. 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 · CSSContainerRule

CSSContainerRule is an interface in idl/cssom.webidl, inheriting CSSConditionRule, 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
Container queries (size)	Widely available	Partial 0.3% 3 of 830 subtests pass	1

Members

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.

• containerName (Container queries (size))
• containerQuery (Container queries (size))