Firebase Auth vs Supabase Auth for Solo Developers

Quick Comparison

Firebase Auth Overview

Firebase Auth is Google's authentication service. It supports email/password, phone verification, anonymous auth, and social providers (Google, Apple, Facebook, GitHub, Twitter). The SDKs handle tokens, refresh, and session persistence automatically. You call a function, and the user is authenticated.

The 50,000 MAU free tier means auth is effectively free for early-stage projects. Firebase Auth integrates deeply with Firestore, where security rules reference request.auth.uid to control access. The mobile SDKs (iOS, Android, Flutter) are excellent and handle platform-specific OAuth flows natively.

I use Firebase Auth for a mobile project. Google Sign-In took minutes to implement with the Flutter SDK. Firestore rules handle authorization. The entire auth-to-database flow required zero custom middleware.

Supabase Auth Overview

Supabase Auth is the authentication layer of the Supabase platform. It supports email/password, magic links, phone auth, and social OAuth. The defining feature is Row Level Security integration, where PostgreSQL policies reference auth.uid() to enforce data access at the database level.

The 50,000 MAU free tier matches Firebase's generosity. User data lives in your PostgreSQL database in the auth schema, which you can query and export. The JavaScript client manages sessions automatically, and the auth UI component library provides pre-built forms.

I use Supabase Auth in a web project where the entire backend is Supabase. Users authenticate, RLS policies activate, and database queries automatically scope to the right user. The integration between auth and database access control is Supabase's strongest feature.

Key Differences

Database model. This is the fundamental difference. Firebase uses Firestore (NoSQL document database). Supabase uses PostgreSQL (relational SQL database). Firebase Auth integrates with Firestore security rules. Supabase Auth integrates with PostgreSQL Row Level Security. If you prefer SQL and relational data, Supabase. If you prefer document-based NoSQL, Firebase.

Data ownership. With Supabase, user data sits in a PostgreSQL database you own. You can query the auth.users table directly, export it, or migrate it. Supabase is also open source, so you can self-host everything. Firebase stores your data on Google's servers. Exporting is possible but manual. Self-hosting is not an option.

Open source. Supabase is fully open source. You can read the code, self-host the entire platform, and contribute fixes. Firebase is closed-source SaaS. If open source matters to you philosophically or practically, Supabase is the only choice here.

Mobile SDKs. Firebase has best-in-class native SDKs for iOS, Android, Flutter, and Unity. The mobile auth experience is polished and handles platform-specific quirks (Apple Sign-In requirements, Google Play Services, etc.). Supabase has JavaScript, Dart, Swift, and Kotlin libraries. They work well, but Firebase's mobile SDKs are more mature.

Anonymous auth. Firebase supports anonymous authentication natively. Users get a temporary account that can be linked to a real identity later. This is powerful for mobile apps where you want users to experience the product before signing up. Supabase doesn't have built-in anonymous auth.

Magic links. Supabase Auth supports passwordless magic link login out of the box. Send an email with a login link, user clicks it, they're authenticated. Firebase can do this with Email Link Authentication, but the setup is more involved. If passwordless email login matters, Supabase handles it more smoothly.

Ecosystem lock-in. Choosing Firebase Auth usually means choosing the Firebase ecosystem: Firestore, Cloud Functions, Cloud Storage. It all works together but ties you to Google. Choosing Supabase Auth means choosing Supabase, but since it's open source, you can self-host or migrate to plain PostgreSQL. The lock-in risk is lower with Supabase.

When to Choose Firebase Auth

• You're building a mobile app (Firebase's native SDKs are best-in-class)
• You prefer NoSQL/document databases (Firestore)
• Anonymous auth for progressive onboarding is important
• You're already invested in the Google Cloud ecosystem
• You need Firebase-specific features (Analytics, Crashlytics, Remote Config)

When to Choose Supabase Auth

• You prefer PostgreSQL and relational databases
• Row Level Security for database-level access control is appealing
• Data ownership and the option to self-host matter
• You want magic link authentication out of the box
• Open source is a priority for your stack decisions

The Verdict

Both Firebase Auth and Supabase Auth are excellent choices for solo developers. They offer identical free tiers (50,000 MAU), simple setup, and deep integration with their respective platforms. The deciding factor isn't the auth layer itself. It's the platform behind it.

If you prefer PostgreSQL, SQL, and relational data modeling, choose Supabase Auth. The RLS integration is powerful, data ownership is real, and the open-source foundation means you're never truly locked in.

If you're building a mobile app or prefer NoSQL, choose Firebase Auth. The native SDKs are more mature, anonymous auth is a real feature advantage, and the Firebase ecosystem (Analytics, Crashlytics, Messaging) adds value beyond just auth.

My recommendation: for web apps, Supabase Auth edges ahead because of PostgreSQL, RLS, and open-source advantages. For mobile apps, Firebase Auth is still the more polished choice. Let your database preference and platform choice guide the auth decision, because these tools are both strong enough that the auth layer won't be the bottleneck.