These charts measure how many WPT tests fail in exactly one browser (of the three major engines - Chromium, Gecko, WebKit), or "Browser Specific Failures". Such tests are interesting as they mostly represent 'real' interop issues in agreed-upon web features.
(Click + drag on graphs to zoom, right click to un-zoom)
Results are from stable releases of browsers at the given date, with a minimal set of flags passed to enable testing.wpt.fyi query
Results are from experimental releases of browsers at the given date, such as Safari Tech Preview. Where appropriate, experimental features are enabled (e.g. --enable-experimental-web-platform-features for Chrome.)wpt.fyi query