[📚] 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