YouTube has revealed it has switched to using HTML5 video by default. The company had already been doing so on certain browsers, including Chrome and Safari, but will now do so even on IE 11 and the latest beta versions of Firefox.
YouTube originally relied on Adobe Flash player to support all its features and be browser independent. Flash, however, is a bit of a resource hog, and also required installing the plugin on most browsers.
To replace Flash, the HTML5 video tag was introduced a few years back but the early versions of the YouTube HTML player lacked features and performed poorly. Thankfully, it has come a long way since then and most people today can’t tell at all if they are on the HTML5 or the Flash player.
Older browsers will continue to use the Flash player as they are unable to handle the new HTML5 standards but the newer ones mentioned above will automatically switch to the HTML5 player. You can find out which player you are on by simply right clicking on the video.