webcompat.com
What it does
A public bug tracker for web compatibility issues. Anyone can file a report when a website behaves incorrectly in a specific browser — broken layouts, missing features, JavaScript errors. Reports are triaged by volunteers and browser vendor employees, then routed to the right browser’s bug tracker. The collected data also feeds into broader compatibility research and helps prioritise fixes.
Who is it for
End users who encounter broken websites and want to report them, web developers diagnosing cross-browser issues, and browser engineers looking for real-world compat regressions to fix.
Where to find it
Who is maintaining it
Mozilla, with contributions from a community of volunteer triagers and participation from other browser vendors including Apple and Microsoft.