This report was prepared to document the current implementation status of the Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) specification as of 31 May 2016 and is based on current test results available in the W3C Conformance Test Harness.
Thirty three user agents, built from ten rendering implementations, were tested across eight operating systems.
The 31 May 2016 revision of the CSS 2.1 test suite was used. The test suite consists of 10389 tests, 241 of which test for optional behavior.
These tests are available in several host language variants:
Some tests only apply to certain language variants; the results for each tested implementation are reported for each tested language variant. Also, not all tests are applicable to each implementation; for example, a browser which implements HTML but not XHTML is not tested for XHTML.
In summary, the results show that 5139 of 10148 tests for required behavior were passed by at least two of the tested implementations. In addition, 193 of 241 tests for optional behavior were passed by at least two of the tested implementations.
Results were gathered from implementation reports submitted by user agent vendors as well as the general public via the W3C Conformance Test Harness.