Gatekeeper is macOS security that checks downloaded apps before first launch. It looks for developer signing and, for many apps, Apple notarization. If an app does not meet those checks, macOS blocks it and shows a warning.
This guide applies to recent macOS versions.
Does This Affect You?
Use this if macOS says an app is from an unidentified developer or cannot be checked for malicious software.
Understand the Warning
- Unidentified developer means the app was not signed with an Apple Developer certificate.
- Apple could not verify the app is free of malware usually means it is signed but not notarized by Apple.
- Gatekeeper checks source and integrity at launch; it is not a full antivirus scanner.
- Only bypass the warning for software you intentionally downloaded from the developer’s real website.
- Delete the app if you do not recognize it or the source feels questionable.
Open a Blocked App You Trust
- Try opening the app once and dismiss the warning.
- Open System Settings > Privacy & Security.
- Scroll to the Security section.
- Click Open Anyway beside the blocked app message.
- Enter your password or use Touch ID.
- Open the app again and choose Open in the final dialog.
Gatekeeper Notes
App Store and Identified Developers
Some macOS versions let you choose whether apps are allowed from the App Store only or from the App Store and identified developers. Open Anyway still approves a specific trusted app.
Approval Is Remembered
After you approve an app, macOS normally allows later launches unless the app is replaced or updated with a different signature.
Verify Before Bypassing
Check the download URL carefully and search the app’s reputation before overriding Gatekeeper. Do not override for random downloads.
Sources
- Apple Support: Open a Mac app from an unidentified developer
- Apple Support: Safely open apps on your Mac
- Apple Platform Security: Gatekeeper