Compiled ungoogled-chromium fails GPU initialization on Windows Server 2016 while official binary works

[rajch3]

Environment

• Build Machine: Windows 11
• Target Machine: Windows Server 2016 (Build 14393.693)
• Visual Studio: 2022
• Chromium Version: 141.0.7390.122
• Repository: ungoogled-chromium-windows (tag: 141.0.7390.122-1.1)

I compiled ungoogled-chromium from source using the official build process (python3 build.py) following the exact
tagged release. The compiled binary fails to initialize GPU/WebGL on Windows Server 2016, while the official
pre-built binary from the same version works perfectly with the same command-line flags.

1. Clone and build:
   git clone --recurse-submodules https://github.com/ungoogled-software/ungoogled-chromium-windows.git
   cd ungoogled-chromium-windows
   git checkout --recurse-submodules 141.0.7390.122-1.1
   python3 build.py

2. Run on Windows Server 2016 with flags:
   chrome.exe --ignore-gpu-blocklist --enable-unsafe-swiftshader --use-gl=angle --use-angle=swiftshader

Expected Behavior (Official Binary)

chrome://gpu shows:
Graphics Feature Status

• WebGL: Hardware accelerated
• WebGL2: Hardware accelerated
• Canvas: Hardware accelerated
• Compositing: Hardware accelerated
  ...

Problems Detected

• WebGPU has been disabled via blocklist or the command line.
• Some drivers are unable to reset the D3D device in the GPU process sandbox
• Disable KHR_blend_equation_advanced until cc shaders are updated

Actual Behavior (Self-Compiled Binary)

chrome://gpu shows:
Graphics Feature Status

• WebGL: Disabled
• WebGL2: Disabled
• Canvas: Software only. Hardware acceleration disabled
• Compositing: Software only. Hardware acceleration disabled
• OpenGL: Disabled
  ...

Problems Detected

• WebGPU has been disabled via blocklist or the command line.
• WebGL2 has been disabled via blocklist or the command line.
• Accelerated rasterization has been disabled
• Accelerated video encode has been disabled
• Accelerated video decode has been disabled
• WebGL has been disabled via blocklist or the command line.
• Gpu compositing has been disabled
• Accelerated 2D canvas is unavailable

Log Messages

[ERROR:components\viz\service\main\viz_main_impl.cc:189] : Exiting GPU process due to errors during initialization
[ERROR:gpu\ipc\service\gpu_channel_manager.cc:925] : Failed to create GLES3 context, fallback to GLES2.
[ERROR:gpu\ipc\service\gpu_channel_manager.cc:936] : ContextResult::kFatalFailure: Failed to create shared context
for virtualization.

Key Observations

1. Official binary works perfectly - WebGL accelerated, no GPU process crashes
2. Self-compiled binary fails - GPU process crashes during initialization, all GPU features disabled
3. Same source code - Both built from identical commit (b477534e7e10d193e916cd4e2967c589383625b2)
4. Same DLL size - chrome.dll is 244MB in both builds
5. --ignore-gpu-blocklist flag has no effect in self-compiled binary
6. Copying GPU DLLs from official to compiled build doesn't help
7. Issue is specific to Windows Server 2016 - Works fine on Windows 10/11 with GPU

Questions

1. Are official binaries built with different compiler flags or on a specific OS version?
2. Is there a known incompatibility when building on Windows 11 for Windows Server 2016 target?
3. Why does --ignore-gpu-blocklist work in official binaries but not self-compiled ones?
4. What could cause GPU initialization to fail in self-compiled but not official binaries from identical source?

Additional Information

• Build configuration used: Default flags.windows.gn + ungoogled-chromium/flags.gn
• Both builds have enable_swiftshader=false in args.gn
• SwiftShader DLLs (libEGL.dll, libGLESv2.dll, vk_swiftshader.dll) are present in both
• The official binary successfully enables SwiftShader-based WebGL on Windows Server 2016
• Self-compiled binary cannot initialize GPU context at all

Any guidance on what might be different between official builds and self-compiled builds that would cause this GPU
initialization failure would be greatly appreciated.

[Lyceris-chan]

from what i can read here its unclear to me whether you used the vscode shell they told us to use in the build guide and i think that may have been where it went wrong im not a dev tho but when i compiled it locally a month ago i had no issues following the guide step by step even modifying the source a little

[rajch3]

Nah. I followed the build instructions to a T. however i sorted it out by compiling and copying chromium.dll to the official branch