Migrate email link sign in away from Firebase Dynamic Links (iOS)

Email link authentication previously relied on Firebase Dynamic Links, which will be shut down on August 25, 2025. We've published an alternative solution in the Firebase Authentication iOS SDK version 11.8.0+. If your app uses Firebase Dynamic Links, you should migrate your app to the new Firebase Hosting based system.

Migrate your associated Firebase Dynamic Links domain to a Firebase Hosting domain

Moving forward, rather than using a Firebase Dynamic Links domain, Firebase Authentication will use the Firebase Hosting default domain for your project to create links for email link and other out-of-band link actions in mobile apps. This means that your app will also need to be updated to use this default domain as the associated domain for email authentication links to your mobile app.

You can follow the instructions in Authenticate with Firebase Using Email Link on Apple Platforms to update your app to use the new automatically provisioned Firebase Hosting default domain.

Use the following instructions to handle links from the new domain and to instruct Firebase Authentication to start using the Firebase Hosting domain to generate mobile app links going forward.

If you'd like to continue using any of your custom Firebase Hosting domains or even your custom Firebase Dynamic Links domain to be your new associated domain, using the instructions in the Customize Mobile Links section, adapt the steps to match the intended domain you'd like to use.

  1. Link Firebase Hosting domain to your app associated domain.

    You'll need to configure the selected domain as an Associated Domain for app links. To set up the entitlement in your app, open the target's Signing & Capabilities tab in Xcode and add Firebase Hosting domains from the previous step to the Associated Domains capability. If using the default Firebase Hosting domain, this will be applinks:PROJECT_ID.firebaseapp.com.

    See Supporting associated domains on Apple's documentation site for more information.

    An associated domain file has been deployed under all your Firebase Hosting domains. To access it, navigate to PROJECT_ID.firebaseapp.com/.well-known/apple-app-site-association. This AASA file can be overwritten; see Create and host your Universal Links configuration files for more information.

  2. Configure your project to use the new links.

    When you're ready to handle the new domain links, you can use the Firebase Admin SDK to update how you want email links to be generated and instruct our backend to start generating links using the new Firebase Hosting domain.

    const updateRequest = {
mobileLinksConfig: {
    domain: 'HOSTING_DOMAIN'
}
}
const updateProjectConfig = () => {
projectConfigManager.updateProjectConfig(updateRequest)
.then((response) => {
    // updated project config
}).catch((error) => {
    console.log('Error updating the project:', error);
});
}

  3. Send and redeem the email link.

    Send the email sign-in link as before. When an end user clicks on the link, they will be redirected to the app if installed to finish the sign in.

You can use a custom Firebase Hosting domain or reuse your custom Firebase Dynamic Links domain to be your new mobile links domain.

Use a custom Firebase Hosting domain

  1. Follow the Firebase Hosting guide to set up a custom domain.
  2. Link the custom domain to your app associated domain.
  3. Send an authentication link to the user's email address with an updated ActionCodeSettings object with a custom domain as linkDomain.
  1. You can re-use any of your Firebase Dynamic Links domains as your custom domain. However, any Firebase Dynamic Links functionality will no longer be supported (for example, users cannot be redirected to the app store if app isn't installed on their device).
  2. Send an authentication link to the user's email address with an updated ActionCodeSettings object with a custom domain as linkDomain.