If you try to open Steam on a Mac and see “steam_osx” is damaged and can’t be opened. You should move it to the Trash, the Steam app or its support files have become corrupted, or macOS’s Gatekeeper security is blocking it. It often appears after a macOS update or an interrupted Steam update. Your games and saved data are usually safe. This guide shows how to fix the error without losing your game library.
Note: steam_osx is the Mac version of Steam. If you play on Windows 11, including Windows running on a Mac through Boot Camp or a virtual machine, you won’t see this message there. See the Windows Steam guides linked at the end instead.
Quick answer
Quit Steam, move the Steam app to the Trash, open ~/Library/Application Support/Steam, and delete everything in that folder except the steamapps folder. Then download a fresh copy of Steam from the official Steam website, drag it into Applications, and open it from there.
Step 1: Quit Steam completely
Press Option + Command + Esc, select Steam if it’s listed, and click Force Quit. Steam can keep helper processes running in the background, so make sure it’s fully closed before changing files.
Step 2: Remove the Steam app
- Open Finder and go to Applications.
- Drag Steam to the Trash.
This removes only the app, not your installed games.
Step 3: Clear Steam’s support files (keep your games)
- In Finder, press Shift + Command + G to open Go to Folder.
- Type ~/Library/Application Support/Steam and press Return.
- Select everything in the folder except steamapps.
- Move the selected items to the Trash.
The steamapps folder holds your downloaded games. Keeping it means you won’t have to download them all again. Many users find that deleting the Steam.AppBundle folder in this location is the key step, since it contains the damaged copy of steam_osx.
Step 4: Reinstall Steam the right way
- Download the latest Steam installer for Mac from the official Steam website.
- Open the downloaded .dmg file.
- Drag the Steam icon into the Applications folder. Don’t run it directly from the disk image or your Downloads folder.
- Eject the disk image.
- Open Steam from Applications and let it update. The first launch downloads fresh support files.
Running Steam from somewhere other than Applications is a common cause of the damaged-app message, because macOS treats apps differently when they’re launched from a downloaded disk image.
Step 5: Allow Steam in Privacy & Security
If macOS still blocks Steam, open System Settings > Privacy & Security. Scroll to the Security section, and if you see a message about Steam being blocked, click Open Anyway and confirm with your password.
Advanced users who have downloaded Steam directly from the official site can also clear the quarantine flag in Terminal with xattr -rd com.apple.quarantine /Applications/Steam.app. Only do this for apps you trust from their official source.
Step 6: Update macOS
Steam drops support for older macOS versions over time. Go to System Settings > General > Software Update and install any available updates, then try Steam again. If your Mac can’t run a supported macOS version, the current Steam client may not work on it.
Other things to check
- Free disk space: Steam needs room to update itself. Free up several gigabytes if your drive is nearly full.
- Restart your Mac: A restart clears stuck background processes.
- Try a different user account: If Steam works in a new macOS user account, the problem is in your account’s Steam files.
- Contact Steam Support: If nothing works, Steam Support can help with your account and client logs.
Are my games safe?
Yes, as long as you keep the steamapps folder. Your purchases are tied to your Steam account, and many games also store saves in Steam Cloud. Even if you delete everything, you can download your games again after signing in.
Playing on Windows instead? See how to download Steam on Windows 10 and how to find the Steam folder on Windows 11.
Related: How to run a Steam game as administrator in Windows 11.
Frequently asked questions
Is steam_osx a virus?
No. It’s the name of the main Steam program on a Mac. The “damaged” message means the file is corrupted or blocked, not that it’s malicious, as long as you downloaded Steam from the official site.
Why did this start after a macOS update?
Updates can change security rules or break older Steam files. Reinstalling Steam usually fixes it.
Do I need to re-download all my games?
No, if you keep the steamapps folder. Steam will find your installed games after you sign in.
Kermit Matthews is a freelance writer based in Philadelphia, Pennsylvania with more than a decade of experience writing technology guides. He has a Bachelor’s and Master’s degree in Computer Science and has spent much of his professional career in IT management.
He specializes in writing content about iPhones, Android devices, Microsoft Office, and many other popular applications and devices.