As announced last year at WWDC, if you notarize your Mac software with the Apple notary service using the altool command-line utility or Xcode 13 or earlier, you’ll need to transition to the notarytool command-line utility or upgrade to Xcode 14 or later. Starting November 1, 2023, the Apple notary service will no longer accept uploads from altool or Xcode 13 or earlier. Existing notarized software will continue to function properly.
The Apple notary service is an automated system that scans Mac software for malicious content, checks for code-signing issues, and returns the results quickly. Notarizing your software assures users that Apple has checked it for malicious software and none was detected.