I thought I wrote a blog post about this before, but it doesn’t look like I did.
We have only been able to offer embedded videos up to 720p resolution and there have been queries asking for higher resolution videos. Well, good news… you can now choose to embed videos up to 8k at 60 fps on your website. The available options depend on the resolution that you uploaded to YouTube. If you uploaded a 720p video, don’t expect to be able to embed the same video in 4k. However, upload a 4k video at YouTube, and you can choose to embed videos on your website with our custom player up to 4k resolution.