Apple Safari has never supported VP8 or VP9, but a move by Google’s YouTube pressures it to do so: Safari users can’t see new 4K videos on YouTube.
Apple Safari is the only current browser that doesn’t support Google’s VP9. In a move that may go a long way towards convincing Apple to do so, YouTube has stopped encoding 4K video in H.264 format, to focus on “delivering the best 4K experience exclusively through VP9.” This means that while YouTube visitors using Chrome, Firefox, Opera and Edge can watch 4K, those running Safari can’t.
Since late December 2016, multiple magazines and blogs have reported that the 4K option has disappeared for new YouTube 4K videos played in Safari. You can see this in the figure below, which is from the Injustice 2 Story Trailer published by YouTube on January 21, 2017. On the left is the quality selector in Chrome, which shows a 4K option, on the right is Safari, which tops out at 1440p.
To verify that YouTube discontinued 4K H.264 encodes, we checked with YouTube, and a company spokesperson shared the comment quoted above. According to the spokesperson, 4K videos already encoded in H.264 will not be removed, and as shown in the figure, 2K videos will continue to be encoded in H.264.
By way of background, Apple has a long history of not supporting VPx codecs. This dates back to Steve Jobs responding to an email asking about VP8 with the URL of a blog post from x264 developer Jason Garrett-Glaser that criticized VP8 for being poorly written and possibly infringing upon H.264’s IP (the blog has since been taken down). Apple is famously in the MPEG LA H.264 and HEVC patent pools, but recently was sued by Nokia for infringing the Finland-based company’s H.264 patents, and may owe HEVC royalties to HEVC Advance. So it wouldn’t be a shock to see Apple dip its toes in the open-source codec waters.
As things stand today, however, if you want to watch 4K videos from YouTube, you’ll need to use a browser other than Safari.