Reproduction steps:
1. Create and open a new project
2. Open the Build Settings (File → Build Settings)
3. Switch the Build Target to WebGL
4. Open the Player Settings
5. Expand the “Publishing Settings” of the WebGL Section
6. Change the Compression Format to “Brotli”
7. Build and Run the project (Build Settings → Build And Run)
8. Observe the opened Build in the Browser

Expected result: The Build runs successfully
Actual result: The Build doesn’t run and is frozen on the “Loading” window

Reproducible with: 2021.3.22f1, 2022.2.13f1, 2023.1.0a19
Not reproducible with: 2020.3.46f1, 2023.1.0b10, 2023.2.0a8
Couldn’t test with: 2021.2.0a21 (Build fails)
Fixed in: 2023.1.0a20

Reproducible on: Windows 10 using Firefox, Windows 11 using Firefox, macOS Ventura 13.1 (Intel) using Firefox 111.0.1 64-bit
Not reproducible: macOS Ventura 13.1 (Intel) using Chrome 111.0.5563.110, Safari 16.2

Notes:
- Could not find regression point due to the Build always failing in alpha versions
- There are a few known workarounds:
First workaround:
1. Install the latest Python version and add the executable to the PATH folder
2. Install the "emrun.py" file from https://raw.githubusercontent.com/juj/emscripten/5dcfc72091fcd2caff0cc26ab92266c18324a975/emrun.py and add it to the project's Build path
3. Open Command Prompt and locate the project's Build path
4. Enter the command "python emrun.py --no_browser --port 8001 ." and in the browser go to the link "localhost:8001"
5. Observe the Player in the browser
Second workaround:
1. Open the Player Settings window (Edit → Project Settings)
2. Select the Player tab
3. In the WebGL Section expand the Publishing Settings tab
4. Change the Compression Format setting to anything other than “Brotli”
5. Build and Run the Project
Third workaround:
1. Open the Build Settings (File → Build Settings)
2. Turn on the “Development Build” setting
3. Build and Run the Project