YouTube has replace Flash with HTML5 as default player. It will now use HTML5 video by default on all modern browsers including Chrome, Safari 8, IE 11 and beta variants of Firefox.
YouTube had announced HTML5 support in 2010. However, it lacked support for Adaptive Bitrate (ABR) that allows more videos with less buffering. This is one reason why it had to continue using Flash. “HTML5’s Encrypted Media Extensions have been somewhat controversial in the web standards community because they enable DRM support in web browsers,”
With HTML5, YouTube will be able to make wider use of Google’s VP9 video codec. This switch will also allow videos to start 15 to 80 percent faster and reduce the required bandwidth to stream a video by 35 percent. “That may not seem like a big deal right now, but once you start streaming 4k video, that 35 percent reduction could be the difference between enjoying the video or staring at the “buffering” screen’” further adds the report.