14 DAY TRIAL // YouTube has had an HTML5 player for years now. More recently, the player has been looking rather good and the site is using it quite often, though only for videos without ads.
The hope has been that YouTube would eventually replace the Flash Player with an HTML5 one.
But that may not be happening anytime soon. In fact, YouTube seems to be making the HTML5 player worse.
Google Operating System noticed that the HTML5 now no longer served 1080p HD videos, even if the original clip is available in the higher resolution. The same videos are available in 1080p via the Flash player.
The change doesn't affect all browsers though, and it is related to the switch to the new adaptive streaming feature YouTube has been working on for the past few years.
Via the new DASH system, the player adjusts the quality of the video depending on network conditions, the player's size, and so on. Likewise, videos are downloaded a few pieces at a time, only a few seconds ahead of the current position.
This system is already used in the Flash player, but in the HTML5 player it requires support for HTML Media Source Extensions, which is only available in Chrome, Opera, and Internet Explorer 11.
If you're using any other browser, you're out of luck. So if you're using the HTML5 YouTube player in Firefox, you will only get videos in 360p and 720p, for now.
YouTube is phasing out these types of streams anyway; it will eventually use adaptive streaming exclusively. Presumably, the HTML5 player will be updated to keep up with the changes.
But it's clear that, for the time being, the Flash Player is the priority. What's more, it will be for the foreseeable future as well. Likewise, don't expect to be able to manually select the quality of the stream for much longer.