I’ve had a lot of people asking me about the digital version of Avengers: Endgame that arrives later tonight digitally across all storefronts. While you can find it in 1080p everywhere, there are a couple of places where you can purchase it in 4K.
Later tonight when the digital version releases, you can purchase it in 4K UHD (with HDR) via Vudu, FandangoNOW, GooglePlay, or Microsoft for $24.99, which is $5 more than the 1080p HD version. The 4K version is not available via iTunes or other digital storefronts…yet.
When Apple rolled out their 4K Apple TV a big deal was made about them selling 4K movies for $20, and at this time Disney does not want to participate in that lower price point. So if you want to be sure to have the 4K version; Vudu, Microsoft, GooglePlay, or FandangoNOW is where to get it. Amazon does often offer the 4K versions of Marvel films, but they don’t have the 4K digital version of Endgame listed for purchase yet. It’s possible they’ll add it after release.
If you do have movies on iTunes, you can link your Vudu and Fandango accounts to it via Movies Anywhere. That will link your purchases across iTunes, GooglePlay, Microsoft, Vudu, Amazon, Fandango, etc. So even if you buy Avengers: Endgame on UHD via Vudu or Fandago, you could still watch the HD version on iTunes or one of the other services.
As for where you can watch your Vudu UHD copy, this thread on the Vudu forums keeps an updated list. Right now the Vudu app will play the UHD movies in 4K with HDR on the Apple TV, Xbox One X/S, the Roku Streaming Stick, the Chromecast, and several smart TVs. The Microsoft digital copy can be viewed on Xbox One S or X, while the GooglePlay version naturally plays on Chrome devices and SmartTVs.