Problem Description
When you download an app from outside the Mac App Store, you often see: "xxx is damaged and can't be opened. You should move it to the Trash" or "Can't open xxx because it's from an unidentified developer".
Why This Happens
Your Mac has a security mechanism that only trusts apps from the Mac App Store or those signed with a developer ID. This blocks legitimate apps that don't have a developer signature.
Solutions
1. Enable "Anywhere" Option
Open Terminal.app, enter the following command and press Enter, then enter your admin password when prompted:
sudo spctl --master-disable
This command allows your Mac to install apps from any source.
2. For macOS Catalina 10.15
Open Terminal.app, enter the following command and press Enter, then enter your admin password:
sudo xattr -rd com.apple.quarantine path-to-app
For example, for Sketch.app:
sudo xattr -rd com.apple.quarantine /Applications/Sketch.app
For CleanMyMac X.app:
sudo xattr -rd com.apple.quarantine /Applications/CleanMyMac X.app
Note: The path like /Applications/Sketch.app is the app's location.
Quick way to get the path: Drag the app into the Terminal window, and the path will appear automatically.
3. For macOS Catalina 10.15.4
After updating to 10.15.4, apps may quit unexpectedly. Use the following method to sign the app.
1. Open Terminal and run:
xcode-select --install
2. Sign the app
In Terminal, run:
sudo codesign --force --deep --sign - (app-path)
Important: Don't miss the space before the path.
3. Troubleshooting
If you see errors like:
/file-location : replacing existing signature
/file-location : resource fork,Finder information,or similar detritus not allowed
First, run this command in Terminal:
xattr -cr /file-location (drag the app in)
Then run the signing command again:
codesign --force --deep --sign - /file-location (drag the app in)
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