I’m trying to enable HDR but I’m getting “Display: Tried to enable HDR display output but unsupported or disallowed, forcing off”
I’m using an HDR display, and Supports HDR Display Output returns true. Tried in 4.25, packaged and in d3d12. Any ideas?
Are you on Windows? Make sure you’re actually using HDR. There may be several other places you need to enable stuff, based on your development environment/hardware/etc. If you’re truly set up for HDR, you should know 
Yes I have HDR enabled in Windows and have seen it working in many games and movies. That’s why I want to see it in my content
Maybe it says it’s unsupported since my TV is below 1000 nits. But I have seen HDR working in other games, I think Unreal games too.
Hey, I was actually searching for a different HDR issue but I saw your question and since I dealt with this recently: are you in fullscreen, and testing in a build? Not windowed fullscreen, but true fullscreen, and not in the editor but in a built game (I don’t remember if it works if you launch your project in game mode, without editor - can test it if you wish).
Edit: oh! And r.AllowHDR needs to be set to 1 e.g. in DefaultEngine.ini. I don’t think it’s documented anywhere, I only found this by digging in UE4 code (see my other post).
For anyone else googling, apparently you can run the editor in hdr too now - not mentioned anywhere but it’s a thing! Running the UE4 editor in HDR - yes it's actually a thing! — Elliot Gray