How to open a Mac app from an “unidentified developer”

You download a Mac app, double-click it, and macOS says it can’t verify the developer. That message is not a virus alert: it means Apple hasn’t reviewed the app. Here is how to decide, and how to open it.

Why macOS shows this

A built-in protection called Gatekeeper checks apps downloaded from the internet. Apps from developers enrolled in Apple’s paid program are notarized: Apple scans them automatically before they ship. Independent developers who haven’t enrolled can’t be vouched for, so macOS warns you. Small, newer apps often fall in this group.

Should you open it?

Only if you trust where it came from. Download from the developer’s own website, and if they publish a checksum, compare it (see below). If you don’t know the source, don’t override the warning.

How to open it

macOS 15 and later

1. Double-click the app. When macOS blocks it, click Done (not “Move to Trash”).
2. Open System Settings › Privacy & Security and scroll to Security.
3. Click Open Anyway next to the app’s name, then confirm with Touch ID or your password.

macOS 14

Right-click (or Control-click) the app in Applications, choose Open, then Open again in the dialog.

macOS remembers your choice, so you only do this once per app.

Check the download first

Developers can publish a SHA-256 fingerprint of their file. Compare it with the one on your Mac:

shasum -a 256 ~/Downloads/Undig.dmg

If both match, the file is exactly the one they published.

Advanced: remove the quarantine flag

This tells macOS to stop treating the file as “downloaded from the internet”. Only use it for a file you have verified:

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

The same steps apply to Undig Cleaner, with pictures, in the first launch guide.