Cascading Style Sheets Official W3C 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

Help wanted

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 are 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.

Test the Web forward:

The “Test the Web forward” project helps organize events where you can participate and write and review tests together with others. TTWF is a project of W3C, with support from Adobe, Facebook and others.


The table below lists some of the available test suites: the latest version, other versions, the next version under development, and the latest test report.

The links under ‘Development’ go to the CSS Test Harness, which generates reports and lets everybody run tests easily. The tests themselves are stored on Github in the Web-platform tests repository.

Specification Latest Release De­vel­op­ment Older Releases
Tests Results Tests Results
Media Queries Release Candidate (1.0) Nightly Report Archive
Selectors Level 3 Final (1.0) Report Nightly Report Archive
CSS 2.1 Final (1.0) Report Nightly Report Archive1)
CSS Basic UI Level 3 None Nightly Report
CSS Color Level 3 Final (1.0) Nightly Report Archive
CSS Marquee Level 3 None
CSS Multi-column Layout None Nightly Report
CSS Namespaces Final (1.0) Report Archive
CSS Paged Media Level 3 Pre-Alpha Archive
CSS Mobile Profile 1.0 Alpha? Archive
CSS Print Profile 1.0 Pre-Alpha Archive
CSS TV Profile 1.0 None
CSS Style Attributes None Nightly Report
CSS Backgrounds and Borders Level 3 None Nightly Report
CSS Conditional Rules Module Level 3 None Nightly Report
CSS Text Decoration Module Level 3 None Nightly Report
CSS Level 1 Obsolete Archive

1) The version used for the CSS 2.1 Proposed Recommendation is the Test Suite of 23 March 2011 and corresponding implementation report.

More development test suites »

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.
Test suite may or may not be complete, but is no longer maintained and is known to contain bugs or is otherwise not recommended for conformance testing.


Unless otherwise stated, all test suites are licensed under both the W3C Test Suite License and the 3-clause BSD License. See W3C Legal's explanation of the licenses.

Contributions to these test suites are governed by the W3C's Policies for Contribution of Testcases to W3C. Contributors who are not members of the CSS Working Group must agree to the terms of Grant II.


Information about the current test submission format and on contributing to the test suites is available on the wiki. Some test authoring guidelines are also available. Our older test suites are written to the principles of the old test suite documentation; please see the wiki for up-to-date information.

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".

Bert Bos, style activity lead
Copyright © 1994–2023 W3C® Privacy policy

Created 13 November 2001. Last updated Tue 12 Sep 2023 09:28:24 PM UTC


About the translations