CSS Testing - QuirksMode.org
FreeCSS tests and browser compatibility research
FreeFree tier
About CSS Testing - QuirksMode.org
QuirksMode CSS is a comprehensive resource for CSS testing and browser compatibility research, maintained by web developer and browser researcher Peter-Paul Koch (PPK). It includes extensive test suites for CSS selectors, properties, values, and units, each accompanied by detailed compatibility tables for desktop and mobile browsers. The site also provides an alphabetical index of all tested features. Originally active from 1999 to around 2014, it served as a key reference for web developers, documenting browser support before tools like MDN and Can I Use became dominant. The site is free, open, and reflects PPK's deep expertise in cross-browser issues.
Key Features
Comprehensive CSS test suites for selectors, properties, values, and units
Browser compatibility tables for desktop and mobile devices
Alphabetical index of all tested CSS features
Covers legacy and modern CSS specifications
Free and open access to all content
Pros & Cons
Pros
- Comprehensive and detailed compatibility tables
- Free and open-source resource
- Authoritative research by a respected web developer (PPK)
- Covers a wide range of CSS features from CSS2 to modern specs
- Historical reference for browser support evolution
Cons
- Site is no longer actively maintained (stopped around 2014)
- Some links may be broken or outdated (e.g., 404 errors)
- Basic design with limited user interface features
- Not updated for recent CSS specifications or browser versions
Best For
Checking browser support for specific CSS properties or selectorsLearning about CSS behavior through practical testsResearching cross-browser compatibility for web developmentVerifying edge cases in CSS rendering
FAQ
What is QuirksMode CSS?
QuirksMode CSS is a website created by Peter-Paul Koch that provides extensive CSS tests and browser compatibility tables. It covers selectors, properties, values, and units, with detailed support data for desktop and mobile browsers.
Who created QuirksMode?
The site is maintained by Peter-Paul Koch, a web developer, browser researcher, and conference organizer based in Amsterdam, the Netherlands.
Is QuirksMode CSS free?
Yes, the site is completely free and open for anyone to use.
Is the site still being updated?
No, Peter-Paul Koch ceased active work on the site around 2014, so the content is not updated for the latest CSS or browser versions.