Symptoms

  • Opening a newly downloaded app shows “… is damaged and can’t be opened.”
  • The app came from a website rather than the App Store.
  • It happened right after moving the app or transferring it between Macs.

What causes “App is damaged and can’t be opened”

  • macOS Gatekeeper quarantined the download because it cannot verify the developer signature or notarization.
  • The download was truncated or the archive was corrupted.
  • The app is genuinely unsigned (older or hobby software).

How to fix it

  1. Re-download the app from the developer’s official site over a stable connection and try again.
  2. If you trust the source, remove the quarantine attribute from the app bundle (command below).
  3. If needed, open System Settings → Privacy & Security, scroll to the blocked-app notice and click “Open Anyway.”

Terminal / CLI command

xattr -dr com.apple.quarantine "/Applications/YourApp.app"

Replace the path with the actual app. Only do this for software you trust from a known source.

How to confirm the fix: The app launches normally and continues to open on subsequent tries.

Prevent it from coming back

Prefer the App Store or notarized downloads, and verify checksums when a developer provides them.