Firebase Auth vs Supabase Auth — When to Pay Google's Tax
Supabase Auth is free and open-source; Firebase Auth charges for basic features. If you're not locked into Google, the choice is obvious.
Supabase Auth
Supabase Auth is completely free with no user limits, while Firebase Auth starts charging at 10,000 monthly active users. Unless you're deep in the Google ecosystem, paying for authentication in 2024 is a choice, not a necessity.
The Philosophy Split: Walled Garden vs. Open-Source Freedom
Firebase Auth is Google's walled garden — it's designed to lock you into their ecosystem with seamless integration to Firebase services like Firestore and Cloud Functions. You're buying convenience at the cost of flexibility. Supabase Auth, on the other hand, is open-source and built on PostgreSQL. It gives you full database access to auth data, letting you write custom SQL queries for user management. This isn't just about auth; it's about whether you want to own your stack or rent it from Google.
Where Supabase Auth Wins
Supabase Auth wins on pricing and control. It's free forever with no limits on monthly active users, while Firebase Auth's free tier caps at 10,000 MAUs before charging $0.0055 per additional user. Supabase also gives you direct database access — you can join auth users with your app data in a single query, something Firebase makes you jump through hoops for. Their Row Level Security integrates natively, so you can secure data at the database level without extra middleware. Plus, it supports Magic Links and Phone auth out of the box without needing to enable a pay-as-you-go plan first.
Where Firebase Auth Holds Its Own
Firebase Auth excels at third-party integrations and enterprise features. It has built-in support for Google, Apple, Microsoft, and 15+ other providers with minimal configuration, while Supabase requires more setup for some. Firebase's Identity Platform (the paid tier) offers advanced features like multi-factor authentication, SAML/SSO, and audit logging that Supabase doesn't match yet. If you're already using Firebase for hosting, databases, or functions, the tight integration reduces development time — you can trigger Cloud Functions on auth events without writing a single line of boilerplate.
The Gotcha: Switching Costs and Hidden Friction
Migrating from Firebase Auth to Supabase Auth isn't trivial. You'll need to export user data (which Firebase makes cumbersome) and handle password hashing differences — Firebase uses bcrypt, while Supabase uses a custom scheme. If you've built features around Firebase's client SDKs, you're rewriting code. Conversely, if you start with Supabase and later need Firebase's enterprise features, you're stuck because Supabase doesn't offer a direct migration path to Google's system. The real friction is vendor lock-in — once you're in Firebase's ecosystem, leaving feels like moving out of a furnished apartment.
If You're Starting Today...
Start with Supabase Auth unless you're building a mobile app with heavy Google services integration. For a web app with a PostgreSQL backend, Supabase gives you free auth, real-time subscriptions, and full database control without a monthly bill. Use Firebase Auth only if you're already committed to Firebase Hosting, Firestore, and Cloud Functions — the convenience might justify the cost. But for greenfield projects, paying for auth when a free, open-source alternative exists is like buying bottled air.
What Most Comparisons Get Wrong
Most reviews treat these as feature-for-feature clones, but they're not. Firebase Auth is a black box — you get what Google gives you, and you can't peek inside. Supabase Auth is transparent — you can inspect the PostgreSQL tables, modify the schema, or even self-host it. The real question isn't "which has more providers?" but "do you want to own your user data?" If you care about portability and cost, Supabase is the only sane choice. If you need enterprise SSO and don't mind Google's pricing, Firebase might be worth it — but know you're paying for the privilege.
Quick Comparison
| Factor | firebase-auth | supabase-auth |
|---|---|---|
| Pricing | Free up to 10,000 MAUs, then $0.0055/user | Completely free, no user limits |
| Database Access | No direct access, requires Admin SDK | Full PostgreSQL access, SQL queries on auth data |
| Third-Party Providers | Google, Apple, Microsoft, 15+ built-in | Google, Apple, Azure, GitHub, more with config |
| Enterprise Features | MFA, SAML/SSO, audit logs (paid tier) | Basic MFA, no SAML, limited logging |
| Real-time Subscriptions | Via Firestore, separate service | Built-in with PostgreSQL changes |
| Self-Hosting | Not possible, Google-cloud only | Full self-hosting with Docker |
| Magic Link Support | Requires Identity Platform ($0.055/user) | Free out of the box |
| Mobile SDK Integration | Seamless with Firebase services | Works but less polished |
The Verdict
Use firebase-auth if: You're building a mobile-first app with heavy Firebase integration and need enterprise SSO features.
Use supabase-auth if: You're starting a web project with PostgreSQL and want free, open-source auth with full data control.
Consider: Auth0 if you need maximum third-party provider support and don't mind paying $0.07 per user — it's the enterprise gold standard.
Supabase Auth is completely free with no user limits, while Firebase Auth starts charging at 10,000 monthly active users. Unless you're deep in the Google ecosystem, paying for authentication in 2024 is a choice, not a necessity.
Related Comparisons
Disagree? nice@nicepick.dev