Firebase Auth errorFirebase Auth: auth/internal-error

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What hides behind auth/internal-error, and the fix

1. 01

   A blocking function threw an error

   “Regardless of whether you use a default or custom message, Cloud Functions wraps the error and returns it to the client as an internal error.” Firebase, Extend Firebase Authentication with blocking functions

   An HttpsError thrown in a beforeUserCreated or beforeUserSignedIn function stops the sign-up or sign-in. Firebase returns it to the app as an internal error, with the function’s message inside, so show that message to the user.

   try {
     await createUserWithEmailAndPassword(auth, email, password);
   } catch (error) {
     console.error(error.code, error.message); // the message holds the reason
     if (error.message.includes('Cloud Function')) {
       showError('Sign-up was blocked. Check the details and try again.');
     }
   }

2. 02

   A blocking function ran past 7 seconds

   “Your function must respond within 7 seconds. After 7 seconds, Firebase Authentication returns an error, and the client operation fails.” Firebase, Extend Firebase Authentication with blocking functions

   A slow database call or outside API in the function can push it past the limit, and every sign-in or sign-up that runs it then fails with an error. Firebase does not say which code that error carries, so read the message. Move slow work to a normal function that runs after sign-up, and keep the blocking function short.

3. 03

   The server hit an unexpected error

   “The error message should contain the response from the Authentication server containing additional information.” Firebase, Admin Authentication API errors (auth/internal-error)

   With no blocking function involved, read the full message from the server. If the same call keeps failing, send the message and the steps to reproduce it to Firebase support.

4. 04

   The app only logs the code

   Also check: an error handler that shows “Something went wrong” and drops error.message hides the cause. Log the message to your error tracker before you change anything else.

Checked against the vendor’s docs on November 9, 2026: Firebase docs: Admin Authentication API errors; Firebase docs: Extend Firebase Authentication with blocking functions; Firebase JS SDK reference: auth error codes.

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Related: Firebase Functions timeout · Firebase auth/operation-not-allowed · Firebase auth/network-request-failed · Firebase auth/billing-not-enabled