Hey, just wanted to make this quick forum post if people are stuck with their WebGL builds getting stuck at 90% in Unity 2020. To fix it I went to Edit - Project Settings - Player - Publishing Settings, and change compression format from Brotli, to disabled. This worked for me so I hope I can help other people with this same issue.
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You really helped me a lot, thank you.
Worked for me too, thanks!
Doesn’t help in fact. Well yes, it can load from my local host this way (when I pick the Build and run option) but when I upload the build to web, it’s always stuck on 90% and that’s all.
(And I’ve tried many tips found online but no one hepled. Now I’m kinda confused… )
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Hey! did you find a solution, I’m having the exact same problem, running on local host but not on website. thanks!
I am also facing the same problem… Working in localhost but not in itch
Same problem here 
Think I’ve tried all possible combination of build setting (player setting).
I had the same 90% problem when trying to run a minimal WebGL scene (cube, light, camera) from Unity 2021.3.11, which ran fine on my local host but not from a remote machine. None of the above fixes helped, and it was likely server configuration. I found that placing the attached file in the /Build folder fixed the problem for me. (remove .txt extension, added for uploading) This modifies the server (in my case IIS) configuration with a few needed mime types.
Hope this helps someone still having this problem. I’m not sure exactly where I found this config file online but it was very helpful so thanks to whomever!
9393248–1314320–web.config.txt (1.25 KB)
Having this issue in Unity 2022.3.17f1 on Unity Play via the WebGL publisher.