Here’s Why Some 4K YouTube Videos Won’t Play in Safari

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It appears as if YouTube no longer supports 4K video playback, in Safari, the default web browser for Mac and iOS devices. 4K resolution, which refers to a horizontal resolution of approximately 4,000 pixels, is currently the “gold standard” in terms of resolution for television shows and movies. Also known as ultra HD (UHD) or 2160p, 4K offers four times the resolution of full-HD / 1080p content. As 4K technology becomes more accessible, and hardware capable of producing a 4K picture becomes cheaper, content in 4K is becoming more widely available – just not currently in Safari, it seems.

The issue was first uncovered in a discussion on popular news aggregation and discussion website Reddit. The author of the original thread, user GezimS, claimed that while he was able to view 4K videos in Chrome without any issues, the same videos offered a max resolution of 1440p when viewed in Safari. The issue seems to only affect videos viewed on the main YouTube site, and doesn’t affect videos that have been embedded into another website.

After a bit of troubleshooting, it was discovered that the issue likely stems from the fact that YouTube is now encoding videos using a different codec, or encoding/decoding format. In April of 2015, YouTube explained in a blog post that they began encoding videos using VP9, a video-coding format developed by Google. According to the blog post, VP9, which is open-source, “brings HD and even 4K (2160p) quality at half the bandwidth used by other known codecs.” VP9 competes with the High Efficiency Video Coding, or H.265 compression standard that has become somewhat standard in the past several years. Unfortunately, Safari doesn’t support the VP9 codec at the moment.

Chrome enabled support for the VP9 codec back in 2013, but Safari has yet to implement the technology. Reddit user themcfly posted an explanation in the original discussion thread:

“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 (at least in my version, still on Safari 9.1 / El Capitan) 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, but is far more hardware demanding to decode…”

As was previously mentioned, the change only seems to affect videos when viewed on the YouTube site. The change also seems to only affect videos that have been uploaded more recently – anything uploaded after December 6th of 2015, according to AppleInsider. However, there is reason to believe that YouTube will continue to encode all future 4K content using the VP9 codec, so until Apple builds support for the codec into Safari, it may be best to switch to Chrome for viewing YouTube videos in the near future.

Featured Image: GongTo / Shutterstock, Inc.
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