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

Fix the macOS Gatekeeper error 'app is damaged and can't be opened' which blocks unsigned or improperly signed applications from launching. This guide covers everything you need to know about this topic, including common causes, step-by-step solutions, and answers to frequently asked questions.

Here are the key things to understand: 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. Understanding these fundamentals will help you diagnose and resolve this issue more effectively.

The most common reasons this occurs include: 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. Identifying the root cause is the first step toward finding the right solution.

To resolve this, follow these recommended steps: Try right-clicking the app > Open (shows an 'Open' button that bypasses Gatekeeper for that app). Remove quarantine: Terminal > xattr -cr /Applications/AppName.app. Verify the download is complete and not corrupted — re-download if necessary. Check System Settings > Privacy & Security for an 'Open Anyway' button after a blocked launch attempt. Scan the app with antivirus before bypassing Gatekeeper to ensure it is not actually malicious. If these steps do not resolve the issue, consider consulting additional resources or a qualified professional.

This article is part of our Mac Error Codes collection on Error Codes Wiki. We provide comprehensive, up-to-date information to help you find solutions quickly.