Steam: "Failed to start game (app already running)"
The game crashed without shutting down cleanly, so a leftover process is still holding its slot and Steam refuses to start a second copy. Open Task Manager, end the game's process, and launch again. If it keeps happening, the game's files are probably damaged — verify them.
Steam tracks whether a game is running by watching its process. When a game crashes silently, the process can survive with no window attached to it. Steam sees something still running and does the sensible thing: it refuses to launch a second instance. Nothing is wrong with Steam, and reinstalling the game will not help until the stuck process is gone.
Symptoms
- "Failed to start game (app already running)" when clicking Play
- The game has no visible window and does not appear in the taskbar
- Steam shows the game as running, or the Play button reads Stop
- It happens every time until the computer is restarted
- It started after the game crashed or was closed with Alt+F4
Why this happens
A crashed game process is still running
A silent crash can leave the executable running with no window. Valve names this as the most common cause of the error.
The game files are damaged
If the game fails to start properly every time, the install itself may be at fault rather than a leftover process — the launch attempt dies immediately and leaves the state behind.
The game is running under another Windows account
On a shared PC with fast user switching, another signed-in account can genuinely have the game open. Valve documents this case explicitly.
A Steam client beta is misbehaving
Beta client builds can introduce launch problems that the stable client does not have.
Fixes
1.End the leftover game process
about 3 minRemoves the exact thing blocking the launch. This is Valve's documented step and it resolves the error immediately in most cases.
Applies to: Windows 10, Windows 11
- Press Ctrl+Shift+Esc to open Task Manager.
- Open the Details tab, or the Processes tab, and find the game's executable — widen the Description column if the name is not obvious.
- Right-click it and choose End task (End Process).
- Confirm if Windows asks, then launch the game from Steam again.
Confirmed by the vendor.
Source: Valve
2.Restart the computer
about 5 minClears any process that Task Manager cannot, including ones held by anti-cheat drivers that refuse to be ended.
Applies to: Windows 10, Windows 11
- Close Steam completely, including from the system tray.
- Restart the computer.
- Open Steam and launch the game before doing anything else.
Confirmed by the vendor.
3.Verify the integrity of the game files
about 20 minIf the error returns every launch, the install is likely damaged and the game is dying instantly. Verifying repairs it without a full reinstall.
Applies to: Steam client on Windows
- Right-click the game in your Steam Library and choose Properties.
- Open Installed Files.
- Select Verify integrity of game files and let it finish.
- Launch the game again.
Confirmed by the vendor.
4.Check whether another Windows account has it open
about 5 minOn a shared PC the game may genuinely be running — just not for you. Valve documents this case.
Applies to: Windows 10, Windows 11
- Open Start and check whether other users are signed in.
- Sign out of every other account rather than just switching away from them.
- Restart the computer and try again.
Confirmed by the vendor.
Source: Valve
5.Opt out of the Steam client beta
about 5 minBeta builds can carry launch bugs the stable client does not. Worth testing if you are enrolled.
Applies to: Steam client on Windows
- In Steam, open Steam → Settings.
- On the Interface tab, find Client Beta Participation.
- Select No beta chosen from the dropdown.
- Choose Restart Now when prompted, then test the game again.
Confirmed by the vendor.
Source: Valve
If none of this worked
If the game launches after you clear the process but crashes again straight away, the launch failure is the real problem and this error is only a symptom of it — the crash is what needs investigating, and Valve directs you to the game's own developer for that. If the stuck process refuses to end in Task Manager, an anti-cheat driver is usually holding it, and only a restart will clear it.
Common questions
- Why does Steam think the game is running when there is no window?
- Because there is still a process. A silent crash can destroy the window while leaving the executable running, and Steam tracks the process rather than the window.
- Will reinstalling the game fix it?
- Not if a stuck process is the cause — the same error returns as soon as you try to launch. Clear the process first; only if the error survives a restart is the install worth suspecting.
Related problems
Sources
Valve · Support page · checked Aug 15, 2026
- Valve states this error is most commonly caused by a game that closed improperly after a silent crash
- Valve documents ending the game's process in Task Manager to clear it
- Valve documents that the game may be running under a different Windows user account
- Valve documents opting out of the Steam client beta as a troubleshooting step
- Verifying game files is documented for when the installation itself is at fault
- Update & Installation IssuesOfficial
Valve · Support page · checked Aug 15, 2026
- Verify Integrity of Game Files is at Library > right-click game > Properties > Installed Files
- Restarting the computer releases locks on files and other resources