Getting files back

The damaged-app error, decoded

Updated 2026-08-08 · 4 min read

The wording says damaged. Nine times out of ten nothing is damaged — macOS is refusing to run something it cannot verify, and the message chooses fear over accuracy.

What is actually happening

Every file downloaded by a browser gets a quarantine attribute. On first launch, Gatekeeper checks the app's signature and notarisation. If the app is unsigned, signed with a revoked certificate, or modified since signing, the launch is blocked — with the damaged-app phrasing.

The same app from the Mac App Store or a notarised installer sails through. The file did not change; the trust chain did.

The legitimate cases

Old software from defunct vendors, open-source tools distributed unsigned, and apps re-downloaded after the developer's certificate lapsed all trip this. If — and only if — you trust the source, two supported paths:

System Settings → Privacy & Security, where a blocked app appears with an Open Anyway button for a few minutes after the failed launch.

Or clear quarantine directly:

xattr -d com.apple.quarantine /Applications/SomeApp.app

That tells macOS you accept the file as-is. It is precisely as safe as your trust in where the file came from.

The cases to respect

Cracked software fails this check *because it was modified* — the crack broke the signature, and the message is finally literal. Installers from mirror sites likewise. Clearing quarantine on those is overriding the one mechanism that would have warned you.

Genuinely damaged downloads

Occasionally the download truly is truncated — an interrupted transfer, a full disk. The tell: the vendor's checksum does not match.

shasum -a 256 ~/Downloads/SomeApp.dmg

Compare against the published hash; a mismatch means re-download, not xattr.

Common questions

Is xattr -d com.apple.quarantine safe?

It is exactly as safe as the file's origin. It disables one warning for one file — appropriate for trusted unsigned software, reckless for software from mirror or crack sites.

Why does the same app work on one Mac and not another?

Quarantine only attaches to downloaded files. Copied over a network or restored from backup, the flag may be absent — so Gatekeeper never ran.