My Mac says the app is damaged. What now?

The dialog shows up a couple of times a year, usually in October, when everything on the laptop updates at once. The file is usually fine. This is the sequence, not a cleaner.

Twice a year the Mac greets a new build with a dialog that says the app is damaged and should be moved to the Trash. The file is usually fine. The dialog is Gatekeeper, and it gets dramatic about anything that arrived through a browser. I am not a security engineer. I am a person who would like to open a photo app before a gallery is due. This is the sequence I actually follow.

What the warning means

macOS keeps a note on files you downloaded. The note says the file came from the internet, and the first open has to be a human agreeing to that. If you double-click and then hit the only button that looks safe, you get the damaged-app story. The file did not become damaged. It became refused. Those are different. A refused app is still the zip you meant to download. A short or corrupt zip is a real problem, and it is less common than the dialog implies.

I check two things before I argue with the window. Did I mean to download this, from the mirror I chose on purpose. And is the zip about the size written on the button. Capture One on this site is about 1.4 GB. PhotoSweeper is about 18 MB. If a "PhotoSweeper" zip is 400 MB, I do not have a Gatekeeper problem. I have the wrong file, and it goes in the Trash without a ceremony.

The Open sequence I use

The words on the dialog move between macOS versions. The gesture has not, on the systems I have used recently.

1. Unzip the download if it is still a zip. You want an app you can see in Finder, not a box inside a box.
2. Drag it to Applications. I do not run tools from Downloads. Downloads is where the wrong zip from last October still lives.
3. Do not double-click it yet. Hold Control, or right-click, the icon in Applications. Choose Open.
4. Read the dialog. The useful button is Open, not Move to Trash. You only do the right-click the first time.
5. If the Mac asks for a password, that is the normal admin password of the machine, the one you already use to install a printer. It is not a fee and it is not a licence key.

After that first Open, a normal double-click is enough. If a later update brings the dialog back, I do the same thing again and I do not take it personally. Point updates have reintroduced the prompt. It is tedious. It is not a verdict on the app.

If the right-click menu has no Open, you are clicking the zip, or an alias, or a file that never unpacked. Go back one step. I have lost ten minutes this way, usually while a gallery upload was also running.

When the quarantine flag is stuck

Sometimes the right-click Open still bounces you back to the same warning. The download note is stuck. Terminal can clear that note. I type this myself. I do not paste a longer command from a forum I found at midnight, including a command from a future version of me who was in a hurry.

Quit the app if it is half open. Open Terminal from Applications, inside Utilities. Drag is safer than typing a path. The command is xattr, and the flag is the quarantine attribute:

xattr -d com.apple.quarantine

Leave a space after that, then drag the app from Applications into the Terminal window so the path is the real path. Press Return. If Terminal answers with silence, that is success. Silence is the house style over there. Then do the right-click Open once more.

If Terminal says there is no such attribute, the file was not stuck that way. Stop. Do not start deleting other attributes because a cheat sheet listed them. I did that once on a font manager and I got to reinstall it on a Sunday, which is not a day I want to meet a font manager.

If it is still stuck

Throw out the copy in Applications and empty that item from the Trash. Download again, from the other mirror if the install dialog had two. A zip can arrive short when the connection drops, and a short zip unpacks into something the Mac is right to refuse. Compare the size to the size on the button. If you are nowhere near the number, you do not have the file.

Still stuck after a clean download and the Open sequence: restart once. Not as folklore. An update is often waiting, and the gate is still using yesterday's rules. If it fails after that, I stop poking. I write to the developer from the contact on their own site, and I say which macOS, which chip, and which mirror. "It won't open" is not a useful letter. "Sequoia, Apple silicon mirror, right-click Open still says damaged, xattr says there is no quarantine attribute" is a useful letter.

What I will not install to get past it

I will not install a cleaner, a Gatekeeper disabler, or a profile a comment thread attached, in order to open a photo app. Those are how a laptop gets slow, and then gets a second cleaner to fix the first one. The utilities on this site are tools I will name. A download link inside a forum reply is not on the list.

I also do not turn Gatekeeper off globally to spare myself the right-click. The prompt is annoying, and it has also been right, once, about a disk image I did not recognise. I want that argument to stay per app. The laptop holds client galleries. Convenience is not worth a standing invitation.

If you arrived from a download button on a program page, the install dialog is the short version. This page is the long version, for when the short version shows you the word "damaged". You do not need both on a normal day.