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User guide

A tour of everything Prefixr does. New to Prefixr? Start with Getting started.

The library

The Library shows your games as cover cards (grid view) or as a compact list (list view); switch with the two buttons next to the sort menu. Search filters by name, and you can sort by name or by runner. Prefixr remembers the view you chose.

Each game shows its SteamGridDB cover if you picked one, otherwise the icon from its .exe.

With a store connected (see Stores), the library also shows that store's games you haven't installed yet, with an Install button instead of the play button. Two more filters then appear in the toolbar: Source (all, added by hand, or one store) and Installed only. Store games carry the store's name on their card.

State What you see
Starting… The launch is being prepared. On first use this includes downloads and setting up the prefix, which can take a few minutes.
Running The game's process runs. The play button turns into a stop button.
Error The launch failed or the game exited with an error. The message and a Show log button appear below the game.

Stop ends the game's whole session: its process tree, the umu container for a Proton game, and the Wine session for a Wine game. Use it when a game hangs. It is the same as closing a game the hard way, so unsaved progress is lost.

The ⋮ menu on a card or in a list row (where editing, artwork and removing also have buttons of their own) has:

  • Show notes: only for a game with notes; see Adding and editing games.
  • Select artwork: see Artwork.
  • Edit game: the same dialog as when adding it.
  • To desktop / To start menu: see Shortcuts.
  • Add to Steam / Update in Steam / Remove from Steam: see Steam integration.
  • Remove: removes the game from the library together with its logs, artwork, shortcuts and settings files. The prefix and the game's files stay. A running game can't be removed.
  • Uninstall (instead of Remove, for a game installed from a store): deletes the game's files as well. It stays in your store library and can be installed again.

Adding and editing games

+ Add game opens the game dialog. The General tab holds what every game needs:

Field Notes
Name Filled in from the .exe's file name (BaldursGate3.exe becomes Baldurs Gate 3). Change it freely.
Program (.exe) The game's executable. Its embedded icon becomes the game's icon.
Prefix Which prefix the game runs in. See Prefixes.
Runner Proton or Wine build to run it with. See Runners.
Environment variables KEY=VALUE, one per line. These win over every switch in the other tabs. WINEDLLOVERRIDES and LD_PRELOAD are added to what Prefixr sets, not replaced.
Launch arguments Passed to the game's .exe, for example --launcher-skip -dx11. Quote arguments with spaces: -path "C:\My Game".
Notes (own tab) Anything worth remembering about the game: an offline login, why a setting is needed, where its config file lives. Show notes in the game's ⋮ menu opens them to read in full, copy from, or go on to edit. A line ending in : shows as a heading, lines starting with - as a list. They're stored as plain text in config.json, so keep real passwords out.

The other tabs (Performance, Graphics, Overlay, and Proton for a Proton runner) override the global settings for this game only. See Game settings.

Installing a game from its setup program

For games that come as an installer:

  1. Right-click the setup .exe in your file manager → Open With → Install Prefixr. Prefixr opens the Install with Prefixr dialog. If Prefixr is already running, the existing window takes over.
  2. Choose a prefix (or create one with +) and a runner, then click Run setup. The prefix is prepared first, exactly as for a game.
  3. Go through the installer. While it runs, the dialog stays open.
  4. When the installer exits, Prefixr scans the prefix's desktop and start menu for shortcuts the installer created. Pick the one that starts the game, or choose the .exe yourself.
  5. The game dialog opens with everything filled in. Check it and click Add.

If no shortcut is found or setup failed, Show setup log shows what the installer printed.

Stores (Epic Games, GOG, Amazon)

Prefixr can install and start the games of your Epic Games Store, GOG and Amazon Games (Prime Gaming) accounts. They appear in the library next to the games you added yourself and run with the same prefixes, runners and settings.

Prefixr talks to each store through the command line tool the Heroic Games Launcher uses for it: Legendary for Epic and gogdl for GOG and Nile for Amazon. A tool is downloaded when you connect its store, at a version pinned in Prefixr and checked against its SHA-256, and deleted again when you disconnect. Like umu-launcher, Legendary and gogdl need Python 3, which almost every distribution has installed; Nile brings its own.

Connecting your account

  1. Open Stores in the sidebar and click Connect next to the store.
  2. Your browser opens the store's login page. Sign in.
  3. Bring the login back to Prefixr and click Sign in:
  4. Epic then shows a short page of text. Copy all of it (or only the value of authorizationCode).
  5. GOG then shows an almost empty page whose address contains on_login_success?…code=…. Copy the whole address from the address bar.
  6. Amazon then shows its homepage, with an address containing openid.oa2.authorization_code=…. Copy the whole address from the address bar.

The code works once and only for a few minutes; if it's refused, open the login page again for a new one.

Prefixr then loads your game list and the covers. Refresh library loads it again, for example after you bought a game. Disconnect signs you out; the games you installed stay installed.

Installing a game

Click Install on a game in the library. The dialog shows the download and installed size and has everything filled in:

Field Default
Install folder ~/Games/Epic, ~/Games/GOG or ~/Games/Amazon on a store's first install, after that the folder you used last for that store. The game gets a folder of its own in it.
Prefix A new prefix for this game alone (recommended), under Prefixr's data folder. Any of your prefixes works too.
Runner Your newest Proton runner.

The download runs in the background; the card shows its progress and has a Cancel button. What was downloaded is kept, so installing again continues where it stopped. Games of one store install one after another. If an install fails, the card shows why, with the install's log.

Once installed, the game is an ordinary library game: you can change its prefix, runner, settings and artwork in the game dialog. Its cover comes from the store; pick another one under Select artwork if you like.

Starting a store game

An Epic game's start asks Legendary for its command line first, because online games need fresh login tokens on it. Without a connection, a game that can run offline still starts. A game's launch arguments go between the game's own arguments and the account's, as in Epic's launcher.

A GOG game needs no login to start: Prefixr starts the program the game's own goggame-<id>.info names as its main one, with its arguments and working folder, just as GOG Galaxy does. Games are installed in English; most let you switch the language in their settings.

An Amazon game starts with what its fuel.json names, in the working folder it asks for. Nile adds the Amazon Games SDK's environment (the entitlement and product the game checks), so Prime Gaming games that ask for it start without the Amazon Games app.

On its first start, a game installs what it lists as prerequisites (Visual C++ runtimes, DirectX and the like) into its prefix. For GOG these are GOG's shared redistributables, downloaded once into Prefixr's data folder for all GOG games; for Amazon, the installers its fuel.json lists under PostInstall. That runs once per game; the launch log shows what happened.

Uninstall removes an Epic game through Legendary, an Amazon game through Nile (the files it installed), and a GOG game's folder (only once it's certain to be the game's: its goggame-<id>.info is in it).

Not supported yet: updating installed games, cloud saves (use your own backup), DLC picked one by one (the DLC you own is installed with the game), GOG's install scripts for a few older games and Galaxy features such as achievements, choosing a game's language, and importing games installed by another launcher.

Prefixes

A prefix is a self-contained Windows environment: its own C: drive, registry and installed programs, separate from your Linux system and from other prefixes.

Adding a prefix

Under Prefixes, choose a folder and click Add prefix:

  • A new or empty folder becomes a new prefix. Nothing is written until the first game or tool runs in it.
  • An existing prefix (a folder with a drive_c inside) is used as it is. That works for prefixes from Lutris, Bottles, PortProton, Heroic or plain Wine.
  • A Steam compatdata/<appid> folder works too: Prefixr uses the pfx folder inside it.

A folder that already contains other files is refused, so a prefix never ends up mixed into unrelated data.

Each prefix shows how many games use it.

Installing dependencies (winetricks)

Install dependencies (📦) opens the winetricks dialog for a prefix. The common packages are listed with a short explanation: the Visual C++ runtimes 2005 to 2022, .NET Framework 4.8, the Windows core fonts, the DirectX shader compiler, D3DX9, XAudio/XACT, DirectShow, PhysX, GDI+ and the Visual Basic 6 runtime. Browse more packages searches all of winetricks' DLL and font packages. Packages already installed in the prefix are marked with ✓.

Pick the runner to install with (it's preselected when all of the prefix's games use the same one) and click Install. Installing downloads the original installers from their vendors and can take several minutes. A Proton runner that ships protonfixes (such as Proton-GE) installs through umu-launcher, inside the same Steam Runtime the game later runs in.

The packages go into the prefix, so they apply to every game using it.

Wine tools

Open Wine tools (🛠️) starts one of Wine's own programs in the prefix:

Tool Use it for
Wine configuration (winecfg) Windows version, DLL overrides, graphics and drive settings
Registry editor (regedit) Editing the prefix's registry directly
Command prompt (cmd) A Windows command line in the prefix
File explorer (winefile) Browsing the virtual C: drive
Task manager (taskmgr) Seeing and ending Windows processes in the prefix
Uninstall programs (uninstaller) Removing programs installed in the prefix

Removing a prefix

Remove only takes a prefix off Prefixr's list. The folder, its programs and save games stay on disk, and games that use it keep working. A prefix whose game is running can't be removed.

Runners

The Runners page lists the runners Prefixr found in its runners folder, each with the number of games using it.

Downloading runners

Download runner shows the recent releases of each source with date and size:

  • Proton-GE (GloriousEggroll), the most widely used Proton build for non-Steam games
  • Proton-CachyOS, the plain x86_64 build
  • Wine (Kron4ek), the staging WoW64 build, which runs 32-bit games without a separate 32-bit Wine

Every download is checked against the checksum file published with the release before it's unpacked.

A runner can be deleted once no game uses it. A runner that is a symlink to another folder only loses the link.

umu-launcher

Proton runners start through umu-launcher. Prefixr keeps its own copy, downloaded the first time a Proton game starts, and shows its version in the umu-launcher section. When a newer release exists, the section offers the update.

The Steam Linux Runtime, which umu downloads on first use (a few hundred MB), is shared with Lutris, Heroic and other umu-based launchers. If one of them already downloaded it, Prefixr reuses it.

DXVK and VKD3D-Proton

Plain Wine builds don't include DXVK (Direct3D 8 to 11 on Vulkan) or VKD3D-Proton (Direct3D 12 on Vulkan). Prefixr downloads the latest release of each the first time a Wine game starts and links them into the prefix on every launch. The DXVK / VKD3D-Proton section shows the versions in use and updates both on request. Proton runners bring their own.

GitHub token

Runner, umu and DXVK lookups use GitHub's API, which allows 60 anonymous requests per hour. If you hit that limit, add a personal access token (no scopes needed) in the GitHub section on the Runners page. It raises the limit to 5000 requests per hour.

Game settings

The four pages under Default for all games (Performance, Graphics, Overlay, Proton) set how every game launches. Each game can override any of them in the matching tab of its game dialog:

  • Changing a value in the game dialog makes it an override for that game, highlighted in the dialog. The tab shows how many overrides it has.
  • The reset button next to an override goes back to the global setting.
  • An override that ends up equal to the global setting is dropped, so the game follows future global changes again.

Performance

Setting Effect Needs
GameMode Raises CPU governor and process priority while the game runs GameMode
Performance power profile Holds the Performance power profile for as long as the game runs, and releases it even if the game crashes power-profiles-daemon
Prevent sleep Keeps the system and screen from sleeping while the game runs systemd-inhibit

If a scheduler daemon that manages process priorities is active (ananicy, ananicy-cpp, scx, scx_loader or falcond), GameMode would fight it over the same settings. Prefixr then skips GameMode and uses the performance power profile instead, and notes that in the game's log.

The page also checks vm.max_map_count. Some games and anti-cheat systems (Easy Anti-Cheat titles, Baldur's Gate 3, Elden Ring, Diablo IV and others) crash when it's low. Values from 1048576, which current Fedora, Arch, Ubuntu and SteamOS ship, count as enough. Below that, Increase now sets Steam's value permanently through a /etc/sysctl.d file (with a password prompt via pkexec). If pkexec isn't available, the page shows the command to run yourself.

Graphics

Gamescope runs the game in its own nested compositor. You can set the width and height it renders at, an FPS limit, and force fullscreen. It's skipped when Gamescope isn't installed or when Prefixr itself already runs inside a Gamescope session (as in Steam's Game Mode).

vkBasalt adds post-processing: Sharpen (CAS), with adjustable strength, and Anti-aliasing (SMAA). Sharpening costs almost nothing and helps when rendering below native resolution.

Overlay

The MangoHud overlay shows FPS, frame times, CPU and GPU load, temperatures and more inside the game. Start from a preset:

Preset Shows
Minimal Just the FPS, tucked into a corner
Standard FPS, load and temperatures at a glance
Detailed Every value, including status icons and technical info such as driver and Wine version
Competitive Large and bold, nothing else

Then adjust which values appear, the position, color, background opacity, rounded corners and a horizontal layout. The preview shows the result. With Gamescope enabled, MangoHud runs as Gamescope's own overlay (--mangoapp) when available.

Proton

These are the switches Proton reads from the environment (PROTON_*). Prefixr reads them from the selected runner's own proton script, so you only see what that runner supports. Each switch has three states: Default leaves the decision to Proton and protonfixes, On and Off force it.

The common switches have a description, for example HDR, the Wayland driver, WineD3D instead of DXVK, updating DLSS, FSR 4 or XeSS, NVAPI, NTSync and Fsync, a per-game shader cache, more memory for 32-bit games, and controllers via SDL. All other switches the runner understands are listed under Advanced.

In a game's Proton tab you also set its protonfixes match (the UMU ID). With the right ID, umu applies the fixes known for exactly that game, and Proton its game-specific tweaks. Search by name: Steam matches come from SteamGridDB (with an API key), the rest from the umu database. Several entries for one game belong to different stores (GOG, Epic, …); pick the store the game came from. You can also type an ID, and a plain Steam app ID such as 1091500 becomes umu-1091500.

Artwork

With a free SteamGridDB API key, entered on the SteamGridDB page, Select artwork finds images for a game:

Kind Used for
Cover The card in Prefixr's library, and the portrait cover in Steam
Icon Desktop and menu shortcuts, and the icon in Steam
Wide cover, Hero, Logo Steam only: the wide grid image, the banner on the game's page, and the logo on it

Search for the game, pick the matching entry, then pick an image for each kind. Images are downloaded once and kept locally. Remove clears one kind again. Prefixr remembers the matched game, so the next time the picker opens straight on its images.

Steam integration

Add to Steam adds the game to Steam as a non-Steam game, with its name, icon and all chosen artwork. It then appears in your Steam library, in Big Picture and in the Steam Deck's Game Mode. Update in Steam writes changes (a new name, new artwork) to the same entry without touching what you changed in Steam itself, such as collections or your own launch options. Remove from Steam takes it out again, and removing a game from Prefixr removes it from Steam as well.

When Steam starts the game, it runs Prefixr with --run <game-id>: the game launches without Prefixr's window, and that Prefixr exits with the game, so Steam shows the game as running exactly as long as it is. This works even while Prefixr is open, and the open window won't start the game a second time.

Steam has to be closed while its shortcuts are changed, because a running Steam would overwrite them. If it's running, Prefixr asks whether to quit it; Steam is started again afterwards. Prefixr keeps the previous shortcuts.vdf as shortcuts.vdf.bak.

Prefixr works with the native Steam package. The Flatpak version of Steam can't start programs outside its sandbox, so it can't launch games through Prefixr.

Shortcuts

To desktop puts a launcher for the game on your desktop; To start menu adds it to your desktop environment's application menu. Both start the game directly (through prefixr --launch <game-id>), opening Prefixr if it isn't running yet. They use the game's SteamGridDB icon if it has one, otherwise the icon from its .exe. Creating a shortcut again replaces the old one, and removing the game removes its shortcuts.

The tray icon

While Prefixr runs, its tray icon offers:

  • Show window / Hide window
  • Quit "game" (force) for every running game, to end one that hangs
  • Quit, which asks first if games are still running, since quitting ends them

Closing the window only hides it to the tray, so running games stay under Prefixr's control. On a desktop without a tray (GNOME without the AppIndicator extension), closing quits Prefixr instead, except while a game runs, when the window is minimized.

Logs

Every game launch writes a log of everything the game and Wine/Proton print. Prefixr keeps the last 10 per game. Setup programs, winetricks and Wine tools write logs per prefix, also the last 10. Open the latest with Show log after an error. All logs are plain text files; see Configuration & files for where they are.

Language

Prefixr is available in English and German. Switch with DE / EN at the bottom of the sidebar; the tray menu follows. On first start, Prefixr uses your system language.

Below the language switch, the sidebar shows Prefixr's version. Click it to see what changed in that version on GitHub.