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Proton is a tool for use with the Steam client which allows games which are exclusive to Windows to run on the Linux operating system. It uses Wine to facilitate this.

Most users should use Proton provided by the Steam Client itself. See this Steam Community post for more details.

The source code is provided to enable advanced users the ability to alter Proton. For example, some users may wish to use a different version of Wine with a particular title.

The changelog is available on our wiki.

Obtaining Proton sources

Acquire Proton's source by cloning and checking out the branch you desire.

You can clone the latest Proton to your system with this command:

git clone --recurse-submodules proton

Be sure to update submodules when switching between branches:

git checkout experimental_6.3
git submodule update --init --recursive

If you want to change any subcomponent, now is the time to do so. For example, if you wish to make changes to Wine, you would apply them to the wine/ directory.

Bulding Proton

Most of Proton builds inside the Proton SDK container with very few dependencies on the host side. For convenience we also provide Vagrant scripts that will create a VM with all the dependencies and a working container runtime and build Proton inside it.

The direct container build is recommended for people building Proton on a regular basis as it is faster and less resource hungry.

The Vagrant VM is easier to set up but comes with higher overhead, which makes it more suitable for an occassional Proton build.

Building with Podman or Docker

Preparing the build environment

You need either a Docker or a Podman setup. We highly recommend the rootless Podman setup. Please refer to your distribution's docummentation for setup instructions (e.g. Arch Podman / Docker, Debian Podman / Docker).

Configuring the build

mkdir ../build && cd ../build
../proton/ --container-engine=podman --enable-ccache --build-name=my_build

Running will create a Makefile allowing you to build Proton. The scripts checks if containers are functional and prompt you if any host-side dependencies are missing. You should run the command from a directory created specifically for your build.

The build by default uses Docker, but you can switch to another, compatible engine with --container-engine=<executable_name>.

You can enable ccache with --enable-cache flag. This will mount your $CCACHE_DIR or $HOME/.ccache inside the container.<version> can be used to build with a custom version of the Proton SDK images.

Check --help for other configuration options.

NOTE: If SELinux is in use, the Proton build container may fail to access your user's files. This is caused by SELinux's filesystem labels. You may pass the --relabel-volumes switch to configure to cause the container engine to relabel its bind-mounts and allow access to those files from within the container. This can be dangerous when used with system directories. Proceed with caution and refer your container engine's manual.



Important make targets:

make install - install Proton into your user's Steam directory, see the install Proton locally section for details.

make redist - create a redistribute build (redist/) that can be copied to ~/.steam/root/compatibilitytools.d/.

make deploy - create a deployment build (deploy/). This is what we use to deploy Proton to Steam users via Steamworks.

make module=<module> module - build both 32- and 64-bit versions of the specified wine module. This allows rapid iteration on one module. This target is only useful after building Proton.

make dxvk / make vkd3d-proton - rebuild DXVK / vkd3d-proton.

Building using Vagrant

This section describes how to use a virtual machine to build proton.

Preparing the build environment

The VM is managed with Vagrant, which you will need to install and configure before invoking these commands. Proton's build system is most well tested with Vagrant's VirtualBox and libvirt/qemu backends. It also requires the vagrant-sshfs plugin. You may run into problems with the shared folder (vagrant_share) and/or CPU and memory usage with other backends.

The Easy Way

We provide a top-level Makefile which will execute most of the build commands for you.

After checking out the repository and updating its submodules, assuming that you have working Vagrant setup, you can build and install Proton with a simple:

make install

You may need to restart the Steam client to see the new Proton tool. The tool's name in the Steam client will be based on the currently checked out branch of Proton. You can override this name using the build_name variable.

See make help for other build targets and options.

If your build VM gets cluttered, or falls out of date, you can use vagrant destroy to wipe the VM clean, then invoke one of the below commands to start over.

The Detailed Way

Proton provides a Vagrantfile, which will automatically set up the Debian VM for you. After installing Vagrant, initialize the VM by running from within the Proton directory:

vagrant up

It will take a long time to download the base image and install all the build dependencies. Eventually it will complete. You can SSH into the virtual machine with:

vagrant ssh

You are now inside a virtual machine with a working Docker setup. At this point you will need to configure and make the build, see building with podman or docker section for details.

mkdir build/
cd build
../proton/ --build-name=my_build

The Vagrantfile is set up to rsync the proton directory into the VM on boot. On the host machine, you can use vagrant rsync-auto to have Vagrant automatically sync changes on your host machine into the build machine. It is recommended that you make changes on your host machine, and then perform the build in the VM. Any changes you make in the proton directory on the VM may be overwritten by later rsync updates from the host machine.

The Vagrantfile also creates a directory called vagrant_share/ in the proton/ directory of your host machine, which is mounted at /vagrant within the VM. You can use this shared folder to move your Proton build out of the VM, or as one way to copy files into the VM.

When you are done with the VM, you can shut it down from the host machine:

vagrant halt

Please read the Vagrant documentation for more information about how to use Vagrant VMs.

Install Proton locally

Steam ships with several versions of Proton, which games will use by default or that you can select in Steam Settings's Steam Play page. Steam also supports running games with local builds of Proton, which you can install on your machine.

To install a local build of Proton into Steam, make a new directory in ~/.steam/root/compatibilitytools.d/ with a tool name of your choosing and place the directory containing your redistributable build under that path.

The make install target will perform this task for you, installing the Proton build into the Steam folder for the current user. You will have to restart the Steam client for it to pick up on a new tool.

A correct local tool installation should look like this:

├── compatibilitytool.vdf
├── proton
├── proton_dist.tar
├── toolmanifest.vdf
└── version

To enable your local build in Steam, go to the Steam Play section of the Settings window. If the build was correctly installed, you should see "proton-localbuild" in the drop-down list of compatibility tools.

Each component of this software is used under the terms of their licenses. See the LICENSE files here, as well as the LICENSE, COPYING, etc files in each submodule and directory for details. If you distribute a built version of Proton to other users, you must adhere to the terms of these licenses.

Runtime Config Options

Proton can be tuned at runtime to help certain games run. The Steam client sets some options for known games using the STEAM_COMPAT_CONFIG variable. You can override these options using the environment variables described below.

The best way to set these environment overrides for all games is by renaming to and modifying it appropriately. This file is located in the Proton installation directory in your Steam library (often ~/.steam/steam/steamapps/common/Proton #.#).

If you want to change the runtime configuration for a specific game, you can use the Set Launch Options setting in the game's Properties dialog in the Steam client. Set the variable, followed by %command%. For example, input "PROTON_USE_WINED3D=1 %command%" to use the OpenGL-based wined3d renderer instead of the Vulkan-based DXVK renderer.

To enable an option, set the variable to a non-0 value. To disable an option, set the variable to 0. To use Steam's default configuration, do not specify the variable at all.

All of the below are runtime options. They do not effect permanent changes to the Wine prefix. Removing the option will revert to the previous behavior.

Compat config string Environment Variable Description
PROTON_LOG Convenience method for dumping a useful debug log to $PROTON_LOG_DIR/steam-$APPID.log For more thorough logging, use
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.
enablenvapi PROTON_ENABLE_NVAPI Enable NVIDIA's NVAPI GPU support library.
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.