# What is Gatekeeper on a Mac? > Gatekeeper is the macOS check that decides whether downloaded software may run. Learn what it checks, why it shows warnings and how it relates to notarization. Canonical: https://www.notchstar.com/glossary/gatekeeper/ Last updated: 2026-11-04 Published 2026-11-04. Gatekeeper is a macOS technology that Apple says ensures only trusted software runs on your Mac. It checks apps you download from outside the App Store, and it is the reason you sometimes see a warning when you open a new app. ## What it checks Apple says that for software from outside the App Store, macOS checks the [Developer ID](https://www.notchstar.com/glossary/developer-id/) signature, which confirms the software comes from an identified developer and has not been altered. By default on macOS Catalina and later it also requires [notarization](https://www.notchstar.com/glossary/notarization/), meaning Apple checked the software for malicious content and found none. Gatekeeper also performs online checks for known malware and for revoked signing certificates. ## Why it matters A warning on a new download is usually Gatekeeper telling you it cannot confirm who made the app or that Apple has not checked it. You can see the verdict yourself in Terminal with `spctl -a -vv /Applications/NotchStar.app`. For a notarized app the answer says `accepted` with a source of `Notarized Developer ID`. ## NotchStar NotchStar is signed with a Developer ID and notarized by Apple since version 1.0.3, released on 9 October 2026. Versions 1.0.0 to 1.0.2 were signed ad hoc, so use the current download. If macOS still warns you, you probably have an older copy. ## Related Read [is NotchStar safe](https://www.notchstar.com/guides/is-notchstar-safe/) for the full checklist, including the permissions each tool asks for. The [Clipboard tool](https://www.notchstar.com/features/clipboard/) shows what the app does after it opens. ## Keep reading. - [What is notarization on Mac?](https://www.notchstar.com/glossary/notarization/): Notarization is Apple's automated check of Mac software before you download it. Learn what Apple says it covers and what it does not. - [What is an Apple Developer ID?](https://www.notchstar.com/glossary/developer-id/): A Developer ID is the certificate Apple gives developers to sign Mac apps shared outside the App Store. Learn what it proves and what it does not. - [Is NotchStar safe? Signing, permissions and what it sends](https://www.notchstar.com/guides/is-notchstar-safe/): NotchStar is signed and notarized by Apple, needs no account and sends nothing unless you opt in. See every permission it asks for and how to check it yourself. - [Clipboard history that lives in your notch](https://www.notchstar.com/features/clipboard/): Searchable clipboard history in the Mac notch: text, links, images and files. Skips password manager copies. Click any item to copy it again. ## More in Security and signing. - [What is notarization on Mac?](https://www.notchstar.com/glossary/notarization/): Notarization is Apple's automated check of Mac software before you download it. Learn what Apple says it covers and what it does not. - [What is an Apple Developer ID?](https://www.notchstar.com/glossary/developer-id/): A Developer ID is the certificate Apple gives developers to sign Mac apps shared outside the App Store. Learn what it proves and what it does not. - [What is a DMG file?](https://www.notchstar.com/glossary/dmg/): A DMG is a disk image, a single file that opens like a drive. Learn how apps ship in one, how to install from it and how to verify the download. - [What is the hardened runtime?](https://www.notchstar.com/glossary/hardened-runtime/): The hardened runtime is a code signing setting that limits what a Mac app can do. Learn what it blocks and how entitlements relax it. - [What are entitlements in macOS?](https://www.notchstar.com/glossary/entitlements/): Entitlements are key value pairs signed into a Mac app that grant it permission to use a service or technology. Learn what NotchStar asks for and why. - [What is the App Sandbox on Mac?](https://www.notchstar.com/glossary/app-sandbox/): The App Sandbox is a macOS feature that limits an app's access to system resources and user data. Learn how it differs from the hardened runtime.