# macOS: “app” can’t be opened because it is from an unidentified developer

**Code:** `"x" can't be opened because it is from an unidentified developer` · **Category:** macOS · **Seen on:** macOS

Gatekeeper refuses to open an app that isn't signed with a registered Developer ID.

## Meaning

Right-click the app and choose Open (the dialog then offers Open), or allow it in Privacy & Security. On recent macOS the control-click trick is hidden for unsigned apps; use System Settings. For your own scripts and tools on the command line, clear quarantine with `xattr`.

## Common causes

- App signed ad-hoc or not at all
- Downloaded from the web (quarantine attribute)
- Old app never updated
- Developer ID certificate expired/revoked
- Packaged by a third party

## Quick fix

1. Right-click → Open
2. Privacy & Security → Open Anyway
3. `xattr -d com.apple.quarantine /path/App.app` only for trusted software

## Detailed fix by platform

### macOS

1. `spctl --assess -vv /Applications/MyApp.app` shows why it's rejected

## How to diagnose

1. **Signature** — codesign -dv output?
2. **Quarantine** — Attribute present?
3. **Trust** — Software trusted?

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Source: [WhatIsMyError](https://whatismyerror.com/errors/macos/unidentified-developer-cannot-be-opened)