(Languages: be de en ru uk)

CSS Conformance Test Suites

Interoperability is the ability of two or more systems or components to exchange information and to use the information that has been exchanged. IEEE

Interoperability is important to web designers. Better interoperability among CSS implementations means designers can write their CSS for one browser and see that it works predictably well on the other browsers. It means reducing the incompatibilities in the way CSS implementations interpret CSS.

Good test suites drive interoperability. They're a key part of making sure web standards are implemented correctly and consistently. More tests encourage more interoperability. Wrong tests drive interoperability on wrong behavior.

CSS needs good test suites! The W3C hosts the official test suites for the CSS Specifications here. Most of these test suites are still works in progress: they're incomplete and may contain errors. You can help us drive CSS interoperability on the Web by reporting errors and contributing test cases. Send questions, comments, error reports, and test submissions to the public-css-testsuite mailing list (or contact fantasai).

Specification Latest Test Suite Prior Versions
Selectors Release Candidate Dated Snapshots
CSS2.1 Pre-Alpha Dated Snapshots
CSS Basic UI Level 3 None None
CSS Color Level 3 Alpha Dated Snapshots
CSS Paged Media Level 3 Pre-Alpha Dated Snapshots
CSS Mobile Profile 1.0 Alpha? Dated Snapshots
CSS Print Profile 1.0 Alpha? Dated Snapshots
CSS TV Profile 1.0 None None

About the Test Suites

Release Phase Definitions

Test suite is complete with no known or suspected bugs. At least two implementations pass, and the specification has reached Recommendation status.
Release Candidate
Test suite is complete with no known or suspected bugs. At least one implementation passes almost all tests.
Test suite has complete coverage of the spec. It may have some bugs but is expected to be mostly reliable. At least one implementation passes a majority of the tests.
Test suite has complete if not thorough coverage of the spec, but is expected to require some revision.
Test suite is incomplete and/or known to contain bugs at time of publication.


Unless otherwise stated, all tests are copyright © W3C and are licensed for use under the W3C Document License. (??) To contribute test cases you'll have to grant W3C a license to publish and modify the tests.


The CSS working group developed a common format for test suites in 2001/2002. It is described in the official CSS test suite documentation. If you want to contribute tests, we advise you to read the authoring guidelines..

Archives and Organization

Test suites are occasionally updated, but old versions remain on-line. If you link to a test suite, you can choose whether to link to a specific, dated version or to the dynamic "current" version.

The URLs of tests for CSS3 modules are of the form:


where MODULE is the (capitalized) module name, e.g., "Selectors", and YYYYMMDD is a date, e.g., "20011105". The "current" link always redirects to the most recent dated test suite.

The URLs of tests for profiles are of the form:


where PROFILE is the name of a CSS profile, e.g., "Mobile" and VERSION is a version number, e.g., "1.0".