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App Is Damaged and Can't Be Opened — Gatekeeper Quarantine Error

Warningsecurity

Overview

Fix the macOS Gatekeeper error 'app is damaged and can't be opened' which blocks unsigned or improperly signed applications from launching.

Key Details

  • Gatekeeper checks application code signatures and notarization before allowing apps to run
  • Downloaded apps get a quarantine attribute that triggers Gatekeeper verification
  • The 'damaged' message often means the app is not notarized, not that it is actually damaged
  • Apple requires all apps distributed outside the App Store to be notarized since macOS Catalina
  • Removing the quarantine attribute bypasses Gatekeeper for that specific app

Common Causes

  • Application not notarized by Apple (developer did not submit for notarization)
  • Application code signature is invalid or was tampered with during download
  • Download was corrupted or incomplete, damaging the app bundle
  • App from a developer not registered in Apple's developer program

Steps

  1. 1Try right-clicking the app > Open (shows an 'Open' button that bypasses Gatekeeper for that app)
  2. 2Remove quarantine: Terminal > xattr -cr /Applications/AppName.app
  3. 3Verify the download is complete and not corrupted — re-download if necessary
  4. 4Check System Settings > Privacy & Security for an 'Open Anyway' button after a blocked launch attempt
  5. 5Scan the app with antivirus before bypassing Gatekeeper to ensure it is not actually malicious

Tags

gatekeeperquarantinedamagednotarizationcode-signing

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Frequently Asked Questions

Usually not. The 'damaged' message is misleading — it most commonly means the app is not notarized or its signature does not pass Gatekeeper's checks. Actual file corruption is less common but possible with incomplete downloads.