CSS resources
The official specs, docs and tools, in one place.
A short, curated list of where CSS is defined, documented and tracked: the W3C and CSS Working Group specifications, MDN's reference, browser support data, and the release notes from Chrome, Firefox and Safari.
Specifications
Where CSS is defined. Editor's drafts show the latest thinking; the W3C pages show what is stable.
- W3CCSS home at the W3CThe W3C's starting point for CSS: news, the list of modules and how the language is developed.
- W3CCSS current workEvery CSS module with its maturity level, from early drafts to finished recommendations.
- W3CCSS Snapshot 2026The official definition of what “CSS” means today: which modules are stable and which are ready to use.
- CSSWGCSS editor's draftsThe live, up-to-date text of every CSS specification, edited as the working group makes decisions.
- CSSWGCSS Working Group on GitHubWhere new features are proposed and debated in public. Anyone can read the issues and join in.
- WHATWGHTML Living Standard: popoverThe HTML side of popovers, the attribute that powers top-layer menus and tooltips.
Reference and learning
The most trusted documentation for every property, selector and function, and structured courses to learn them.
- MDNMDN: CSSMozilla's CSS documentation home, with guides for every part of the language.
- MDNMDN: CSS referenceAn A to Z of every property, selector, at-rule and value, each with examples and a compatibility table.
- MDNMDN: CSS guidesIn-depth guides by module: grid, flexbox, colors, animations, anchor positioning and more.
- MDNMDN: CSS styling basicsA beginner course covering selectors, the box model, the cascade and how to debug CSS.
- MDNMDN: CSS layoutA course on normal flow, flexbox, grid, floats, positioning and responsive design.
- web.devLearn CSSA free course from the Chrome team, from the box model to logical properties and functions.
Browser support
Check whether a feature works in the browsers your visitors use before you ship it.
- web.devBaselineA clear yes or no on whether a feature works across all major browsers, and since when.
- W3C WebDXWeb Platform StatusSearchable Baseline status and test results for every web feature, kept up to date automatically.
- CommunityCan I useDetailed support tables by browser version, with usage statistics and known issues.
- WPTInterop 2026The yearly effort by browser makers to fix the same features everywhere, with live scores.
- W3C WebDXweb-featuresThe open data set behind Baseline, for tools and linters that check your CSS.
From the browser makers
Release notes and blogs where new CSS features are announced first.
- ChromeChrome for Developers: CSS and UIArticles and guides on new CSS in Chrome, often with demos.
- ChromeChrome Platform StatusWhat Chrome is building, shipping or removing, feature by feature.
- WebKitWebKit blogSafari's release notes and deep dives on new CSS features.
- WebKitWebKit feature statusThe status of every web feature in WebKit, the engine behind Safari.
- MozillaFirefox release notes for developersWhat changed in each Firefox release for CSS, HTML and JavaScript.
- web.devweb.dev blogMonthly roundups of what landed in browsers, and what reached Baseline.
Tools for writing and debugging CSS
Validators and the browser developer tools for inspecting layouts, colors and animations.
- W3CCSS Validation ServiceCheck a stylesheet for errors against the official CSS grammar.
- ChromeChrome DevTools: CSSInspect and edit styles, debug grid and flexbox, and work with colors and animations.
- MozillaFirefox DevToolsFirefox's inspector, with grid, flexbox and font tools that many designers prefer.
- WebKitSafari Web InspectorSafari's developer tools for debugging on macOS, iPhone and iPad.
Accessibility
CSS decides color contrast, focus styles, motion and reading order, so it shapes who can use a page.
Put it into practice
Free tools from this site that turn these specs into something you can see and use.