Fix Sequoia "App is Damaged" Error
Trying to open an app on macOS Sequoia only to be told it "is damaged and can't be opened"?
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The Symptom
This usually happens with apps downloaded outside the App Store. It is rarely a "damaged" file and usually a Gatekeeper flag issue.
The Fix
- Strip the Quarantine Attribute
If you trust the app, you can manually remove the "danger" flag in Terminal:
sudo xattr -rd com.apple.quarantine /Applications/AppName.app
- Re-sign the Application Locally
If the developer's certificate has expired, you can ad-hoc sign it on your own Mac:
codesign --force --deep --sign - /Applications/AppName.app
- Check the Gatekeeper Status
Go to System Settings > Privacy & Security. Scroll to the bottom and see if the app is listed there with an "Open Anyway" button.
Pro Tip
Never run the xattr command on apps you don't recognize. This bypasses macOS's primary malware protection.