Why axe and IBM Disagree, Tested Against W3C ACT Rules
I put the same page into two checkers. One says “needs review.” The other says “fail.” If your team has used more than one automated accessibility checker, you’ve probably seen this. So which one is right? I decided to answer that with numbers. The 37 accessibility test rules that W3C has approved come with 558 approved examples, each one labeled with the correct answer: this HTML passes, this HTML fails. I ran them through axe-core and IBM Equal Access, one by one. Of the 430 cases both tools checked, 413 agreed on whether the example fails (407 if you count “cannot tell” as its own result). The 17 that split were mostly cases where one tool returned cannot tell, or where one tool failed code that ACT doesn’t consider a failure. ACT rules are the yardstick for this comparison. The format they’re written in, ACT Rules Format 1.1, became a W3C Recommendation, W3C’s name for an official web standard, in February 2026. ...