Fix 'App Is Damaged' Error on macOS (Quick Steps)

Quick answer

Open Terminal and run xattr -dr com.apple.quarantine /path/to/App.app, then relaunch the app.

Why this happens

The 'App is damaged and can't be opened' error is almost never about actual file corruption. It's macOS's Gatekeeper security system flagging an app that was downloaded from the internet or transferred from another Mac. When you download an app outside the App Store, macOS attaches a quarantine attribute. If the app was built with an older signing certificate or the developer didn't notarize it properly, Gatekeeper gets jumpy and throws this misleading message.

I've seen this on Intel Macs and Apple Silicon Macs alike, from Mojave all the way through Sonoma. It's especially common when you download apps from GitHub releases or direct links from a dev's site—sites that aren't App Store verified. The fix is simple: strip that quarantine flag so Gatekeeper backs off.

Fix steps

Quit the app if it's open. If it won't quit normally, use Force Quit (Cmd+Option+Esc).
Open Terminal (Finder > Applications > Utilities > Terminal).
Type xattr -dr com.apple.quarantine (note the space at the end).
Drag the app from Finder into the Terminal window. The full path will appear, like /Applications/MyApp.app.
Press Return. You won't see any output if it worked.
Try opening the app again. If it still complains, go to System Settings > Privacy & Security and click 'Open Anyway' next to the app's name.

If that doesn't work

Sometimes the quarantine flag isn't the only issue. Here are the next things to try:

Reboot your Mac – Sounds dumb, but caches get stuck. A fresh restart clears out stale Gatekeeper state.
Re-download the app – Delete the app completely (drag to Trash), empty the Trash, then download it again. Maybe the original download was actually corrupted (rare, but happens).
Check your security settings – Go to System Settings > Privacy & Security. Look for a message about the app being blocked. If it's there, click 'Open Anyway'. You'll get a warning dialog—click 'Open' to override.
For apps from unknown developers only – If you're on macOS Catalina or earlier, you can also right-click the app and select 'Open' from the context menu. That triggers the override prompt directly.

Prevention

To avoid this in the future, download apps from the Mac App Store or from developer sites that properly notarize their apps. But if you're a tinkerer who grabs tools from GitHub (no shame—I do it weekly), you can skip the headache by clearing the quarantine flag right after you unzip the app. Make it a habit:

xattr -dr com.apple.quarantine ~/Downloads/MyApp.app

Do that before you move it to your Applications folder, and you'll never see that damn 'damaged' message again. I keep this command in a text snippet on my phone, that's how often I use it.

One more thing – if you're on Apple Silicon and the app still won't open after all this, check if it's a universal binary. Some older apps are Intel-only and Rosetta 2 might be missing. Install Rosetta by running softwareupdate --install-rosetta in Terminal, then try again.