Google’s built-in testing tool Lighthouse judges the accessibility of our websites with a score between 0 and 100. It’s laudable to try to get a high grading, but a score of 100 doesn’t mean that the site is perfectly accessible. To prove that I carried out a little experiment.
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Manuel Matuzovic wrote a web page that’s pretty-much inaccessible to everybody: it doesn’t work with keyboard navigation, touchscreens, or mice. It doesn’t work with screen readers. Even if you fix the other problems, its contrast is bad enough that almost nobody could read it. It fails ungracefully if CSS or JavaScript is unavailable. Even the source code is illegible. This took a special kind of evil.
But it scores 100% for accessibility on Lighthouse! I earned my firework show for this site last year but I know better than to let that lull me into complacency: accessibility isn’t something a machine can test for you, only something that (at best) it can give you guidance on.