Why isn't my video showing in 4K on YouTube
LumaFusion exports 4K video per industry standards in either H.264 or H.265 format, with many options. Google works with all of these options and it processes uploaded videos to their own preferred formats. Their preferred encoding and its compatibility with browsers and devices determines what resolutions will be seen in any context. If you are not seeing 4K, either the device or browser is incompatible with Google's 4K encoding or YouTube hasn't finished encoding the 4K streams.
After upload from LumaFusion completes, YouTube begins its processing of the video into multiple formats. This takes time and often the 4K stream will only be available in 4K compatible browsers after at least 20 minutes or more. 4K uploads from LumaFusion both at H.265 and H.264 will be available for viewing where Google’s 4K codec (VP9) is supported, such as on the Chrome browser.
Until this issue is resolved by Google or Apple, we recommend that you upload 4K videos for sharing to Vimeo.
Google uses 4K encoding that is not supported by Apple's Safari browser on the MacOS or any other iOS browser that uses Apples WebKit framework—that is, all major iOS browsers including Google's Chrome for iOS. The highest video resolution you may see in an iOS browser for any 4K YouTube video is usually 1080p. The YouTube app on iOS may show resolutions as high as 1440p but often is limited to 1080p. The same video can be viewed at the full 4K resolution in the chrome browser on a PC or Mac. The browser incompatibilities with Safari are widely known and began in Jan 2017. Still today, a 4K video on YouTube will show at resolutions up to 1440p but often only at 720p or 1080p in Safari.