How to Fix Steam Failed to Start Game (App Already Running)
Open Task Manager (Ctrl + Shift + Esc), find the game's executable under 'Background processes', and click 'End task'.
Preliminary Fast Checks
Verify these 3 simple prerequisites before proceeding to in-depth fixes:
đŦ Root Cause: Why Does App Already Running Occur?
When a game exits abnormally or crashes silently, its Windows process thread can remain frozen in the background holding memory handles. Because Steam monitors active PID handles, it refuses to launch a second instance.
đ Primary Triggers for App Already Running
- Game crashed silently during shutdown and left an orphaned process.
- Steam Cloud Sync stalled while uploading save games to Valve servers.
- Third-party software hook (Discord overlay, GeForce Experience) keeping the process handle open.
What NOT to Do
Never delete game save files to fix this error; the issue is strictly a stuck background OS process.
Complete Step-by-Step Solutions for App Already Running
Execute these verified methods sequentially from easiest to most advanced:
Kill Zombie Game Process in Task Manager
Directly terminate the lingering game executable from memory.
Press Ctrl + Shift + Esc > Details tab > sort by Name > locate the game executable (e.g. cs2.exe, dota2.exe) > right-click and select 'End process tree'.
Restart the Steam Client Completely
Forces Steam to refresh all active process hooks.
Click Steam (top left) > Exit. Open Task Manager and ensure 'steam.exe' is closed, then relaunch Steam as Administrator.
Verify Integrity of Game Files
Fixes corrupted game launch manifests that cause games to hang during launch.
Right-click the game in Steam Library > Properties > Installed Files > click 'Verify integrity of game files'.
đĄ How to Prevent App Already Running In the Future
- Always exit games via their in-game main menu rather than Alt + F4.
- Disable Steam cloud synchronization temporarily for games with buggy cloud sync.
Frequently Asked Questions
If a specific game always stays open in the background, an overlay hook (like Discord or MSI Afterburner) is failing to unhook on game exit. Disable the overlay.