Software, browsers & email

App can't be opened because it is from an unidentified developer

This macOS message blocks apps that aren't notarized by Apple, which is common with smaller or free apps and doesn't necessarily mean the app is unsafe. A one-time override in system settings lets you open it if you trust the source.

Difficulty
Easy
Time
5 minutes
DIY cost
$0

Symptoms

  • Message saying macOS cannot verify the developer
  • App won't open with a double-click
  • Prompt to move the app to Trash
  • App works after right-clicking and choosing Open

Likely causes

  • CommonApp isn't notarized by AppleSmall developers or open-source apps often skip Apple's notarization process.
  • CommonApp was downloaded outside the App StoremacOS applies extra scrutiny to apps not from the App Store.
  • PossibleGatekeeper security setting set to strictSystem security settings control how cautious macOS is about new apps.
  • Less commonApp is genuinely unsafeOccasionally this warning correctly flags malicious software.

What to do

  1. Only proceed if you trust the source you downloaded the app from.
  2. Right-click (or Control-click) the app and choose Open, then confirm Open in the dialog that appears; this bypasses the block for that app only.
  3. If that option isn't available, go to System Settings > Privacy & Security and click 'Open Anyway' next to the blocked app message.
  4. Re-download the app if you're unsure the file wasn't corrupted or tampered with.
  5. Verify the developer or publisher is legitimate before opening if you have any doubt.

When to call a pro

If you're unsure whether an app is safe, don't open it — ask someone knowledgeable or the software's official support first.

Safety

Use caution

Only override this warning for software from a source you trust; it exists to protect you from malicious apps.

Related guides

Operator provides AI-generated troubleshooting information. It can be wrong. For safety-critical, electrical, gas, structural, medical, automotive safety, or other high-risk problems, consult a qualified professional.