Firebase Auth vs SuperTokens
Pricing
Firebase Auth: Free up to 50k MAU (phone auth: 10k/mo free)
SuperTokens: Free self-hosted, managed from $0 (up to 5k MAU)
Description
Firebase Auth: Google's authentication service with generous free limits and tight integration across the Firebase ecosystem
SuperTokens: Open-source authentication you can self-host for free or use their managed service
Pros
- 50,000 monthly active users free: most solo products never hit that ceiling
- Google, Apple, GitHub, and 10+ social providers work out of the box
- Plugs directly into Firestore, Cloud Functions, and other Google Cloud services
- Fully open source (Apache 2.0): inspect every line, fork it, no vendor lock-in
- Self-hosted option means zero recurring cost for auth, ever
- Pre-built login UI with session management, MFA, and social login
Cons
- Tied to the Google ecosystem: using Firebase Auth without other Firebase services feels awkward
- Custom UI required: no pre-built login components like Clerk offers
- Migrating user password hashes out of Firebase is possible but painful
- Self-hosting requires running a Java backend service alongside your app
- Smaller community and fewer integrations compared to Auth0 or Clerk
- Documentation covers the basics but thins out for advanced customization
Details
Firebase Auth handles email/password, social login, phone auth, and anonymous users with minimal setup. Google gives you 50,000 MAU free for most auth methods, which is five times what Clerk or Auth0 offer. If you are already using Firestore or Cloud Functions, Auth plugs in with a single line of config.
The downside is that Firebase Auth is designed to keep you inside Google’s ecosystem. Using it as a standalone auth service (say, with a Postgres database and a Next.js app on Vercel) is doable but clunky compared to Clerk or Supabase Auth. You also need to build your own login UI, since Firebase only provides a basic drop-in widget (FirebaseUI) that looks dated. For solo founders already committed to Firebase, Auth is the obvious choice. For everyone else, evaluate whether you want that Google dependency.
SuperTokens is an open-source auth provider that gives you a real alternative to paying per-user fees. Self-host the SuperTokens core (a Java service) alongside your app, and you get email/password, social login, passwordless, session management, and MFA without paying anyone anything. The managed version is free up to 5,000 MAU if you do not want to run infrastructure.
The tradeoff is operational complexity. Self-hosting means you own the auth infrastructure: updates, monitoring, backups. The core service runs on Java, which adds a dependency some teams would rather avoid. If you are building a product where long-term auth costs matter (high user count, thin margins), SuperTokens can save you thousands per year. If you just want auth working in an afternoon and do not mind paying Clerk or Auth0 later, those are faster to set up.
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