[📚] Critical: Firebase Email Link Authentication dependency on Dynamic Links facing deprecation in 2025

[eli1stark]

Firebase Dynamic Links (FDL) will be deprecated on August 25, 2025, as stated in the official documentation:

• https://firebase.google.com/docs/dynamic-links
• https://firebase.google.com/support/dynamic-links-faq

Critical Impact:
The Firebase Authentication's "Sign in with Email Link" feature currently relies heavily on Firebase Dynamic Links. Specifically, the implementation requires a Firebase Dynamic Links domain in the actionCodeSettings:

const actionCodeSettings = {
  // URL you want to redirect back to. The domain (www.example.com) for this
  // URL must be in the authorized domains list in the Firebase Console.
  url: 'https://www.example.com/finishSignUp?cartId=1234',
  // This must be true.
  handleCodeInApp: true,
  iOS: {
    bundleId: 'com.example.ios'
  },
  android: {
    packageName: 'com.example.android',
    installApp: true,
    minimumVersion: '12'
  },
  dynamicLinkDomain: 'example.page.link'
};

Current Limitations:

• Attempting to use a custom domain (non-FDL) results in an error
• The feature doesn't work without a valid FDL domain

Questions:

1. What is the migration path for Email Link Authentication after FDL deprecation?
2. Will there be an alternative mechanism to handle email link authentication?
3. Why isn't there a deprecation warning in the Email Link Authentication documentation?

Reference:
Email Link Authentication documentation: https://firebase.google.com/docs/auth/flutter/email-link-auth

[SelaseKay]

cc @russellwheatley

[ysak-y]

https://firebase.google.com/docs/dynamic-links says Email Link Authentication still works after FDL is deprecated.

I'm currently using or need to use Dynamic links for email link authentication in Firebase Authentication. Will this feature continue to work after the sunset?
Yes, your email link authentication using Firebase Authentication will continue to work.

Firebase Authentication currently uses Firebase Dynamic Links to customize Authentication links, but we will provide an update that will require a client- side update to ensure that email link auth continues working after the Firebase Dynamic Links service is shut down.

Note that Firebase Authentication only depends on the Firebase Dynamic Links service internally, but does not depend on the Firebase Dynamic Links SDK.