CSS2.1 Conformance Test Suite

This is the test suite that was used to prove the interoperability of CSS level 2 revision 1 and advance the Proposed Recommendation of 12 April 2011 to Recommendation. The implementation report documents the support as it was on 10 April 2011.

Tests are not normative. Some tests in the test suite may contain errors. Please check the latest version of the CSS2.1 specification and its errata before assuming a failure is due to an implementation bug and not a test suite bug.

The appropriate mailing list for submitting tests and bug reports is public-css-testsuite@w3.org. More information on the contribution process and test guidelines is available on the wiki page.

Tests are available in three formats:

XHTML 1.1 tests sent as application/xhtml+xml
HTML 4.01
HTML 4.01 tests sent as text/html
XHTML 1.1 for Printers
XHTML 1.1 tests with all images converted from PNG to JPEG and formatted with headers and footers to ease testing of embedded printer software. This is not a canonical format, and some tests may fail due to the format conversion that would otherwise pass in the above XHTML 1.1 format.

Additional tests, that do not fit in any of those formats, are located separately:

Other Formats
Tests that do not fit in the above formats because they test a combination of CSS and a particular document language's features and/or error recovery.

Unless the test instructions explicitly indicate otherwise, any occurrence of red in a test indicates test failure.

Note that many of the tests require the Ahem font to be installed. These tests are marked with the 'ahem' flag in their metadata. Without the Ahem font installed, these tests are of no value.

Some of the font-related tests also require special fonts. These tests are marked with the 'font' flag in their metadata.

Implementation Reports

An implementation report template is available to help with creating implementation reports. See also the explanation of its format.

Common Assumptions

Most of the test suite makes the following assumptions:

Uncommon Assumptions

In addition, some of the tests make one or more of the following assumptions:

The tests that need these assumptions to be true have not yet been marked, but it is likely that we will add a way to identify these tests in due course. Tests should avoid relying on these assumptions unless necessary.


This test suite is licensed under both the W3C Test Suite License and the W3C 3-clause BSD License. See W3C Legal's explanation of the licenses.


Many thanks to the following for their contributions:

...and all the contributors to the CSS1 test suite.