Thanks a lot @dbcarlton I can confirm your 2 sentences about Return URLs if usePopup: true: 1 - redirectURI must be "https://example.com" (without any path) in app config 2 - "https://example.com" must be added in return URLs in Apple Developer website Moreover let me add my own finding: 3 - do NOT add any 'alert("my debug message")' (you might have done for debugging as in my case) in the listener "AppleIDSignInOnSuccess". An alert in that listener will prevent the Apple popup to close.