How to Fix macOS CodeSign Not Signed Errors — App Not Opening

In this tutorial, you'll learn about How to Fix macOS CodeSign Not Signed Errors. We cover key concepts, practical examples, and best practices.

The Problem

Your macOS app shows:

"App" is damaged and can't be opened.

or:

code signing failed: No identity found.

Quick Fix

Step 1: Check the code signing identity

security find-identity -v -p codesigning

If empty, you have no signing certificates installed.

Step 2: Sign the app

codesign --force --deep --sign "Developer ID Application: Your Name (TEAMID)" /path/to/App.app

Step 3: Verify the signature

codesign -dv --verbose=4 /path/to/App.app

Step 4: Fix resource fork issues

xattr -cr /path/to/App.app
codesign --force --deep --sign - /path/to/App.app

Step 5: Remove quarantine attribute

xattr -d com.apple.quarantine /path/to/App.app

Step 6: Create a self-signed certificate

security create-keychain -p temp temp.keychain
security add-certificates -k temp.keychain
# Then use Certificate Assistant to create a self-signed certificate
# Select: Keychain Access > Certificate Assistant > Create a Certificate

Prevention

• Always sign apps before distribution.
• Use Developer ID certificates for outside-the-Mac-App-Store distribution.
• Keep signing certificates in the login keychain.

Common Mistakes with codesign not signed

1. Using return to exit a function early instead of wrapping a pure value in the monad
2. Mixing let bindings with <- bindings in do notation, producing type errors
3. Overlapping type class instances that cause GHC to reject the program with ambiguous dispatch errors

These mistakes appear frequently in real-world MACOS code. DodaTech's contributors have identified these patterns through analysis of open-source projects and production systems.

Practice Exercise

Write a pure function that safely divides two integers using Maybe, then test it with edge cases like division by zero and negative numbers.

This exercise reinforces the concepts covered in this guide. Try implementing it before checking online solutions.

FAQ