macOS "App is Damaged" Warning: Why It Happens and How to Fix It

macOS uses a security mechanism called Gatekeeper to protect users from malicious software. Gatekeeper requires applications downloaded from the internet to be signed with an Apple Developer certificate. If an app is not signed or notarized by Apple, macOS marks it as "damaged."

OpenGnothia is an open-source and free project. Apple Developer Program membership costs $99 per year, which may not be sustainable for volunteer-driven open-source projects. Therefore, the application is currently not signed with an Apple certificate.

This warning does not mean the application is actually damaged or malicious. It is a standard security warning that macOS gives to every unsigned application downloaded from the internet. OpenGnothia's source code is completely open and can be reviewed on GitHub.

Gatekeeper is one of macOS's built-in security features. Since macOS Catalina (10.15), security policies have been further tightened. Gatekeeper operates at three levels: apps downloaded from the App Store (most trusted), signed apps from identified developers, and apps from unknown sources.

When you download a file from the internet, macOS adds a special attribute called com.apple.quarantine (an extended attribute) to the file. When the app is first opened, Gatekeeper checks this attribute and evaluates the application's trustworthiness.

For unsigned apps, Gatekeeper may show two different warnings: "[App] can't be opened because Apple cannot check it for malicious software" or the more severe "[App] is damaged and can't be opened. You should move it to the Trash." The second warning is particularly common on macOS Ventura and later.

To fix this issue, you simply need to remove the quarantine attribute that macOS added to the file. This operation is safe and only clears the quarantine flag on the downloaded file.

Step 1: Open the Terminal application. Press Command + Space to open Spotlight, type "Terminal", and press Enter.

Step 2: Paste the following command into Terminal and press Enter:

xattr -cr /Applications/OpenGnothia.app

If you haven't moved the app to the Applications folder and it's still in Downloads, use this command instead:

xattr -cr ~/Downloads/OpenGnothia.app

Step 3: After running the command, you can open OpenGnothia normally. The application will work without any issues.

The xattr command is used to manage extended attributes on files in macOS. Here's what the flags in our command mean:

The -c flag: Clears all extended attributes from the file (clear). This includes the com.apple.quarantine attribute.

The -r flag: Applies the operation to subfolders as well (recursive). A .app file is actually a folder structure, so we need to clear all sub-files too.

This command only modifies file attributes — it does not affect the application itself or your system settings. It is completely safe to use.

If you prefer not to use Terminal, you can also try to resolve the issue through macOS System Settings, although this method may not always work.

Step 1: Try to open OpenGnothia and receive the warning.

Step 2: Go to System Settings > Privacy & Security.

Step 3: Near the bottom of the page, you'll see a message like "OpenGnothia was blocked from use because it is not from an identified developer." Click the "Open Anyway" button next to it.

Step 4: Another confirmation dialog will appear — click "Open."

Note: If you're getting the "is damaged" warning, this method may not work. In that case, you'll need to use the Terminal method.

I ran the xattr command but it still won't open, what should I do? Make sure you used the correct file path. Verify that OpenGnothia.app exists in the location by running ls /Applications/ in Terminal. Also make sure you dragged the app from the DMG file to the Applications folder.

Is this safe? Yes, the xattr -cr command only removes the quarantine attribute from the file. It does not modify the application's code or your system security settings. OpenGnothia is open source and all its source code can be reviewed on GitHub.

Do I need to do this after every update? Yes, every time you download a new version from the internet, macOS adds a new quarantine attribute. So you may need to run the xattr command again after each update.

Does this issue occur on Windows or Linux? No, this issue is specific to macOS's Gatekeeper mechanism. You won't encounter this warning on Windows or Linux.