Firebase Authentication is Google's hosted identity service, offering email/password, phone, and social login backed by Google's infrastructure. It's simple to set up, but it's closed source, ties your user data to Google's platform, and pushes you toward the rest of the Firebase/Google Cloud ecosystem as your app grows.
Hanko is an open-source alternative if you want to own your authentication stack and self-host rather than depend on Google's infrastructure.
FAQ
Is there a free, open-source alternative to Firebase Authentication?
Yes. Hanko is open source (AGPL-3.0) and can be self-hosted instead of relying on Google's infrastructure.
What's the best open-source alternative to Firebase Authentication?
Hanko is the best fit if you want passkey-first login and full control over where user data lives, instead of Firebase's Google-hosted model.
What are the top open-source alternatives to Firebase Authentication?
Browse all open-source alternatives to Firebase Authentication above, or explore the full Security category for more options.