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Bugs Killed

Mac

An app I downloaded will not open because Apple cannot check it for malicious software

You double-click an app you downloaded and macOS refuses, saying it cannot check the app for malicious software, or that the developer cannot be verified. This is Gatekeeper doing its job. Apple documents a supported way to open an app you trust, and a very different answer for an app macOS says will damage your computer.

Affects

Versions

  • macOS Catalina and later

Apps

  • Apps downloaded from outside the App Store

What you see

  • An alert says Apple cannot check the app for malicious software, with Move to Trash and Done buttons
  • An alert says "the app developer cannot be verified"
  • An alert says the app "wasn't downloaded from the App Store"
  • Control-clicking the app and choosing Open no longer gets past the alert

Why it happens

Confirmed By default, macOS Catalina and later require software to be notarized. When the developer ID cannot be verified, or the app was never notarized, Apple puts it this way: "macOS can't verify that the app is free of malware". [1]

Confirmed In macOS Sequoia, Apple removed the Control-click shortcut that used to override Gatekeeper. MacRumors reported that people must instead open System Settings and go to the Privacy and Security section to "review security information" before the software will run. [2]

When it shows up

The alert says Apple cannot check the app, or that "the app developer cannot be verified", and the app came from a source you trust

You are in this case if:

  • The alert offers Move to Trash and Done, and does not say "the app will damage your computer"
  • You downloaded the app from the developer's own site or a link you asked for
  • The app is not in the App Store, or the App Store copy is older

2 fixes below

The alert says "the app will damage your computer", or macOS moved it to the Trash

You are in this case if:

  • The alert names malware rather than an unverified developer
  • macOS offers to send a copy of the app to Apple
  • The app is already in the Trash

1 fix below

The alert says the app "wasn't downloaded from the App Store"

You are in this case if:

  • The alert names the App Store rather than a developer or malware
  • System Settings > Privacy & Security > Security is set to allow apps from the App Store only

1 fix below

The steps that killed it

The steps are behind a quick check

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Keeping it away

  • Download apps from the App Store or the developer's own site, so notarized builds open with no warning.
  • Treat an unexpected malware alert as real, rather than looking for a way around it.

Sources

  1. Safely open apps on your Mac
    Apple Support, 2026-05-27
  2. macOS Sequoia Makes It Harder to Override Gatekeeper Security
    MacRumors, 2024-08-06

Last verified 2026-09-14