Fixing “app is damaged” on a Mac you share with an iPad

You downloaded a utility, double-clicked it, and macOS announced it was damaged and should be moved to the Trash. Most of the time the file is fine and the quarantine flag is the whole story. Here's the order I actually use, from least dramatic to the one people paste into the wrong forum.

Check you opened the app, not the disk image

A lot of "damaged" reports are a disk image that didn't finish copying, or an app launched from inside the image instead of from Applications. Drag it to Applications, eject the image, and try again from the folder you actually trust. If the iPad downloaded the archive into iCloud Drive and the Mac opened it before the file finished arriving, wait for the cloud to stop spinning. A half file is genuinely damaged. The dialog isn't always wrong.

Allow it in Privacy & Security

Try to open the app once, so macOS records the refusal.
Open System Settings, then Privacy & Security.
Scroll until you see the note about the app being blocked, and choose Open Anyway.
Confirm with the password or Touch ID. macOS will ask one more time when the app launches.

This is the path I want people on. It leaves a decision in Settings instead of a terminal command nobody will remember next year.

Clear the quarantine flag

If Settings has no button and you are sure of the download, the quarantine attribute is the usual culprit. In Terminal, from the folder that contains the app:

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

Replace the path with the app you actually have. Don't point it at a random disk. Don't run a version of this you found under a YouTube video with sixteen steps and a "disable all protection" flourish. One attribute, one app, then try again.

When it really is damaged

If the image won't open, the checksum the developer published doesn't match, or the same build fails on a second Mac, download it again. A file that took a trip through a flaky sync is allowed to be broken. Delete the bad copy so you don't keep opening it from Recents on either device.

I keep this page because the same dialog shows up under half the utilities in the catalog, and I don't want to paste it into every review. When a specific app has a weird extra step, that step lives on the app's page.