Firebase Auth errorFirebase Auth: auth/missing-or-invalid-nonce with Sign in with Apple

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Why Firebase rejects the nonce, and the fix

1. 01

   The hashed nonce went to Firebase

   “You will send the SHA256 hash of the nonce with your sign-in request, which Apple will pass unchanged in the response.” Firebase, Sign in with Apple (iOS)

   The most common mix-up: the app passes the hash to both sides. Apple gets the hash; Firebase gets the original string.

   final rawNonce = generateNonce(); // your own helper: a random string per sign-in
   final hashed = sha256.convert(utf8.encode(rawNonce)).toString();
   final apple = await SignInWithApple.getAppleIDCredential(
     scopes: [AppleIDAuthorizationScopes.email, AppleIDAuthorizationScopes.fullName],
     nonce: hashed,
   );
   final credential = OAuthProvider('apple.com').credential(
     idToken: apple.identityToken,
     rawNonce: rawNonce,
   );
   await FirebaseAuth.instance.signInWithCredential(credential);

2. 02

   No nonce was sent to Apple

   “Firebase validates the response by hashing the original nonce and comparing it to the value passed by Apple.” Firebase, Sign in with Apple (iOS)

   Without a nonce in the Apple request, the ID token has nothing for Firebase to compare. Always set the nonce on the Apple request.

3. 03

   The nonce changed between request and sign-in

   Generating a new nonce after the Apple sheet opens, or keeping it in a widget that rebuilt, breaks the match. Keep the raw nonce from that attempt until signInWithCredential finishes.

4. 04

   The hash is not a hex string

   Also check: Firebase’s sample asks for the SHA256 hash as a hex string. Base64 or raw bytes won’t match what Firebase computes.

Checked against the vendor’s docs on November 9, 2026: Firebase docs: Sign in with Apple (Apple platforms).

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Related: Firebase auth/credential-already-in-use · Firebase auth/operation-not-allowed · Firebase account-exists-with-different-credential · Firebase missing initial state