WebM is in development – http://dev.modern.ie/platform/status/webmcontainer/Justin DynamicD commented
Adding m voice that until it can run basic .webm behind a video tag it's not really supported. It's a smooth browser otherwise, but this is litterally a deal breaker for many many people.
2,652 votesJustin DynamicD commented
Adding my support to this idea. The release cycle for Edge is unacceptable. Decouple it from Windows 10 and let it get updated as it's own project.