A recent discussion on Reddit has brought to light the news that YouTube no longer has the 4K video playback option when using Safari. The change may have come after a long ago announcement that YouTube began encoding uploaded videos into VP9. The change seems to affect recently uploaded videos, and thus so far only seen on the main YouTube site and not within embeds.
After a reddit user began wondering why he was no longer seeing a 4K option under Safari, other users began chiming in with different ideas on why that might be happening. Recently, /u/themcfly helped point out some specific changes as to what was happening:
Upon further inspection, I discovered that Youtube stores different kinds of video on their servers, encoded either in VP9 or the older H264 codec. Safari has no VP9 support…so it gets automatically served a H264 version from Youtube (you can verify codec by right clicking > stats for nerds). Chrome supports VP9 so gets served that version…
For some context, Chrome enabled VP9 video codec support back in 2013, while Safari still hasn’t. In April of 2015, YouTube posted an update to their Engineering and Developers Blog explaining the advances the VP9 video codec would be bringing.
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