Supabase Auth vs Firebase Auth: Best Free Auth for Startups
Supabase Auth vs Firebase Auth 2026 — free tier MAU limits, RLS integration, mobile SDKs, pricing, and which free auth service is best for startups.
Quick Answer
Supabase Auth wins for SQL-based apps: 50K free MAUs, Postgres RLS integration, and full self-hosting option. Firebase Auth is better for mobile-first apps (Android/iOS SDKs are more mature) and teams already on the Firebase/GCP stack. The key differentiator is the database: if you use Postgres, choose Supabase; if you use Firestore, choose Firebase.
Supabase Auth vs Firebase Auth: Overview
SQL-based apps, Next.js, startups on Supabase, self-hosted deployments
50,000 MAUs free on hosted; unlimited on self-hosted
Pro plan $25/month; Auth included in all plans
Supabase Auth vs Firebase Auth: Feature Comparison
| Feature | Supabase Auth | Firebase Auth |
|---|---|---|
| Free Email/OAuth MAUs | 50,000 MAUs | Unlimited |
| Free SMS OTP | None (Pro required) | 10,000/month |
| RLS / DB Integration | Native Postgres RLS | Firestore rules only |
| Self-Hosted Option | Yes (Docker Compose) | No |
| Mobile SDK Maturity | Good (growing) | Excellent (8+ years) |
| Enterprise SSO | SAML (Team plan) | SAML (Google Cloud Identity) |
Pros & Cons
Supabase Auth
Pros
- 50K MAU free tier — 5x Firebase's phone auth free limit and more generous than most competitors
- RLS integration: auth.uid() available in Postgres row-level security policies natively
- Self-hostable: full Supabase stack (including Auth) runs on your own VPS via Docker Compose
- SSO via SAML 2.0: enterprise SSO included in Team/Enterprise plans without add-on fees
- Passwordless: magic links, OTP, OAuth (GitHub, Google, Apple, 20+ more) all built in
Cons
- Mobile SDKs lag behind Firebase: Flutter and Android Supabase Auth SDK are less battle-tested
- No phone SMS auth on free tier: phone OTP requires $25/month Pro plan upgrade
- Auth UI: GoTrue-based; no prebuilt React component library (use Auth UI or build custom)
- Rate limits on free tier: 30 emails/hour for magic links — tight for viral growth spikes
Firebase Auth
Pros
- Free unlimited email/OAuth MAUs: no MAU cap for email and social login — scales for free
- Mature mobile SDKs: Android, iOS, Flutter SDKs with 8+ years of production hardening
- Google Sign-In: one-tap and automatic sign-in deeply integrated with Google Play Services
- Phone auth: 10,000 free SMS verifications/month with global carrier coverage
- Multi-factor auth: TOTP and SMS MFA available on Blaze (pay-as-you-go) plan
Cons
- Vendor lock-in: Firebase Auth tightly coupled to Firebase/GCP ecosystem — hard to migrate
- No self-hosted option: all auth flows go through Google infrastructure — no on-prem
- SMS costs scale: 10K free SMS/month then $0.0055/SMS — 100K SMS = $495/month
- Firestore-native: integrating Firebase Auth with Postgres (not Firestore) requires extra work
Our Verdict: Supabase Auth vs Firebase Auth
Supabase Auth is the better choice for web startups using Postgres — native RLS, 50K free MAUs, and self-hosting give it a clear edge over Firebase for server-rendered apps. Firebase Auth wins for mobile-first teams (especially Flutter and Android) and anyone who needs free SMS OTP at scale. Use Supabase Auth if your stack is Next.js + Postgres; use Firebase Auth if you are building a mobile app or already invested in Firestore.
Supabase Auth vs Firebase Auth — FAQs
Does Supabase Auth integrate with Postgres Row Level Security without extra code?
Yes — this is Supabase Auth's biggest advantage over Firebase. When a user authenticates, Supabase sets the auth.uid() Postgres function to return that user's UUID for the duration of the database session. You can write RLS policies like "auth.uid() = user_id" directly in your table definitions, and Supabase automatically enforces them on every query through the REST API or SDK. Firebase Auth requires you to manually pass user tokens and validate them server-side because Firestore Security Rules are a separate system from any SQL database.
Can I migrate from Firebase Auth to Supabase Auth without making users reset passwords?
Partially. Firebase Auth allows you to export users with password hashes (using scrypt with Firebase's custom parameters). Supabase's GoTrue auth server supports importing hashed passwords, but you must match the hashing algorithm. Firebase uses a modified scrypt that is compatible with Supabase's import tool. OAuth-only users (Google, GitHub sign-in) migrate cleanly — just re-link providers. Phone auth users will need to re-verify via SMS. In practice, a migration takes a weekend sprint with testing, not months.
Is Supabase Auth suitable for apps expecting 1 million users?
Yes, but you will need to upgrade from the free tier. The $25/month Pro plan is unlimited MAUs for auth (Supabase does not charge per MAU on paid plans — the 50K limit is a free-tier guideline, not a hard cap). Above that, the Team plan at $599/month adds priority support and higher rate limits. Firebase Auth at 1M users costs nothing for email/social login but SMS costs can be significant. Self-hosting Supabase on a dedicated VPS removes all MAU limits entirely and is a viable path for high-scale applications.
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