| | `PROTON_LOG` | Convenience method for dumping a useful debug log to `$PROTON_LOG_DIR/steam-$APPID.log` For more thorough logging, use `user_settings.py`. |
| | `PROTON_LOG_DIR` | Output log files into the directory specified. Defaults to your home directory. |
| | `PROTON_DUMP_DEBUG_COMMANDS` | When running a game, Proton will write some useful debug scripts for that game into `$PROTON_DEBUG_DIR/proton_$USER/`. |
| | `PROTON_DEBUG_DIR` | Root directory for the Proton debug scripts, `/tmp` by default. |
| | `PROTON_WAIT_ATTACH` | Wait for a debugger to attach to steam.exe before launching the game process. To attach to the game process at startup, debuggers should be set to follow child processes. |
| | `PROTON_CRASH_REPORT_DIR` | Write crash logs into this directory. Does not clean up old logs, so may eat all your disk space eventually. |
| `wined3d` | `PROTON_USE_WINED3D` | Use OpenGL-based wined3d instead of Vulkan-based DXVK for d3d11, d3d10, and d3d9. |
| `nod3d11` | `PROTON_NO_D3D11` | Disable `d3d11.dll`, for d3d11 games which can fall back to and run better with d3d9. |
| `nod3d10` | `PROTON_NO_D3D10` | Disable `d3d10.dll` and `dxgi.dll`, for d3d10 games which can fall back to and run better with d3d9. |
| `noesync` | `PROTON_NO_ESYNC` | Do not use eventfd-based in-process synchronization primitives. |
| `nofsync` | `PROTON_NO_FSYNC` | Do not use futex-based in-process synchronization primitives. (Automatically disabled on systems with no `FUTEX_WAIT_MULTIPLE` support.) |
| `noxim` | `PROTON_NO_XIM` | Enabled by default. Do not attempt to use XIM (X Input Methods) support. XIM support is known to cause crashes with libx11 older than version 1.7. |
| `nativevulkanloader` | | Use the Vulkan loader shipped with the game instead of Proton's built-in Vulkan loader. This breaks VR support, but is required by a few games. |
| `forcelgadd` | `PROTON_FORCE_LARGE_ADDRESS_AWARE` | Force Wine to enable the LARGE_ADDRESS_AWARE flag for all executables. Enabled by default. |
| `heapdelayfree` | `PROTON_HEAP_DELAY_FREE` | Delay freeing some memory, to work around application use-after-free bugs. |
| `gamedrive` | `PROTON_SET_GAME_DRIVE` | Create an S: drive which points to the Steam Library which contains the game. |
| `noforcelgadd` | | Disable forcelgadd. If both this and `forcelgadd` are set, enabled wins. |
| `oldglstr` | `PROTON_OLD_GL_STRING` | Set some driver overrides to limit the length of the GL extension string, for old games that crash on very long extension strings. |
| `vkd3dfl12` | | Force the Direct3D 12 feature level to 12, regardless of driver support. |
| `vkd3dbindlesstb` | | Put `force_bindless_texel_buffer` into `VKD3D_CONFIG`. |
| `hidenvgpu` | `PROTON_HIDE_NVIDIA_GPU` | Force Nvidia GPUs to always be reported as AMD GPUs. Some games require this if they depend on Windows-only Nvidia driver functionality. See also DXVK's nvapiHack config, which only affects reporting from Direct3D. |
| | `WINE_FULLSCREEN_INTEGER_SCALING` | Enable integer scaling mode, to give sharp pixels when upscaling. |
| `cmdlineappend:` | | Append the string after the colon as an argument to the game command. May be specified more than once. Escape commas and backslashes with a backslash. |
| `nowritewatch` | `PROTON_NO_WRITE_WATCH` | Disable support for memory write watches in ntdll. This is a very dangerous hack and should only be applied if you have verified that the game can operate without write watches. This improves performance for some very specific games (e.g. CoreRT-based games). |
| `seccomp` | `PROTON_USE_SECCOMP` | **Note: Obsoleted in Proton 5.13.** In older versions, enable seccomp-bpf filter to emulate native syscalls, required for some DRM protections to work. |
| `d9vk` | `PROTON_USE_D9VK` | **Note: Obsoleted in Proton 5.0.** In older versions, use Vulkan-based DXVK instead of OpenGL-based wined3d for d3d9. |