CSS SOTA

Scan CSS source and report every feature in it that does not meet a browser support target. Targets are either a Baseline level ("baseline-widely", "baseline-newly") or an explicit browser list ("chrome 120, safari 17.4, firefox 128"). Reports the offending line, what is wrong (unsupported, too old, prefix-only, partial), and the minimum version that would work. Browserslist queries like "last 2 versions" are not supported. IMPORTANT when reading Baseline-level results: Baseline describes a whole feature, and a feature can be "Limited" because one part of it is not interoperable while the exact declaration you wrote works everywhere. "Cursor styles" is Limited, so cursor: pointer is reported — yet it only lacks iOS Safari, where a cursor is meaningless rather than broken. Each finding therefore also names the browsers missing that specific key, or says that the key ships everywhere and the status comes from elsewhere in the feature. Read that line before removing anything: a key that ships everywhere is still not proof the code works, since it may be inert without the parts that do not.

Look up which browser versions support a CSS property, value, selector, at-rule or function, from MDN browser-compat-data bundled with this server (no network call). Give either a BCD key ("css.properties.anchor-name") or a property with an optional value ("display" + "grid"). Also reports vendor prefixes, partial implementations and the Baseline status of the feature the key belongs to.

UI/UX guidelines and a review of a page against them. mode="guidelines" returns the principles — Nielsen's 10 heuristics, Hick's and Fitts's laws, WCAG 2.2, neurodiversity-inclusive design, motion and microinteractions (including when Lottie or Rive are worth their bundle cost), SVG craft and animation, light-first theming, lightness and responsiveness — optionally filtered by topic. Read them BEFORE designing or building UI. mode="review" statically reviews supplied HTML and CSS, or a URL, and reports what violates which principle. The review reads source and does not render it, so it cannot measure computed contrast, real target sizes, or where focus lands — it catches what is visible in the markup, which is most of what actually goes wrong.

Get everything known about one CSS feature: Baseline status and dates, the browser versions it shipped in, its description, spec links, Web Platform Tests scores, usage, and MDN reference prose. Accepts a web-features id ("container-queries") or a display name ("Container queries"). Use search_css_features first if you do not know the id.

Search CSS features on the Web Platform Dashboard (webstatus.dev) by keyword, Baseline status, and the date range in which they reached Baseline. Use this to answer questions like "which CSS features for scroll animations are Baseline yet?" or "what limited-support CSS is there for anchoring?". Returns live Baseline data. For the browser versions a specific property shipped in, use check_support instead.

List CSS features that crossed a Baseline threshold within a date range, newest first. Use this to answer "what CSS can I start using now?", to write release notes, or to catch up after time away. Defaults to the last 180 days. The date is when a feature became interoperable across browsers, which is usually well after it first shipped in one.