If you’re a Safari user, you may have noticed you can no longer stream the most recently uploaded 4K YouTube videos in their native resolution via your Mac’s default browser.
The issue was first raised almost a month ago by Reddit user GezimS, who wondered why the option to view 4K videos in 2160p was no longer available.
Other Reddit users confirmed they too could not stream at 4K, but only when the UHD content had recently been uploaded. They also noted that accessing the same video in Firefox or Chrome allowed them to view it at the video’s highest 2160p resolution.
After some digging, user themcfly recently discovered that the issue is being caused by a change to the way YouTube encodes video and serves it through its website.
YouTube looks to be storing their video in either the more efficient VP9 codec, or the older, but more established H.264 codec. Safari only supports H.264, so newer videos stored in the VP9 format can’t be played in the highest resolution. Safari users are limited to 1440p resolution as their highest viewing option.
MacRumors’ report notes the newer videos CAN be streamed at 4K if they are embedded on another site. The VP9 codec support requirement apparently only kicks in when the videos are viewed directly from the YouTube site.
Apple will likely add VP9 codec support in a future update to Safari, but until then, you’ll have to use Chrome or Firefox to view 4K video in its native resolution from the YouTube site.