Supabase Auth vs Firebase Auth: Open Source vs Google BaaS

Overview

Supabase Auth is the authentication layer of Supabase, the open-source Firebase alternative built on PostgreSQL. It is powered by GoTrue, an open-source auth server originally built by Netlify, and integrates directly with Supabase's Postgres instance to enable row-level security policies keyed on authenticated user IDs. Firebase Auth is Google's production-grade auth service designed for mobile and web applications, offering the deepest integration with the broader Firebase platform.

Both services target developers building applications who want auth handled without building it from scratch. The philosophical divide is significant: Supabase is committed to open source and data portability, while Firebase is a closed Google platform where your data and users live in Google's infrastructure. This distinction has real implications for data sovereignty, self-hosting, and long-term portability.

Key Technical Differences

Supabase Auth's killer feature in the context of the Supabase stack is Row Level Security (RLS) integration. You can write Postgres policies like auth.uid() = user_id that automatically filter query results based on the authenticated user, all enforced at the database level. This eliminates an entire class of authorization bugs that plague applications with application-layer access control. The auth tokens are JWTs that Postgres can verify natively, making the integration zero-overhead.

Firebase Auth's strength is its mobile SDK quality. The Android and iOS SDKs are deeply integrated with platform-native capabilities — Google Sign-In on Android uses the native credential manager, Apple Sign-In on iOS uses the native framework, and phone authentication uses Firebase's global SMS infrastructure with carrier-grade deliverability. For consumer mobile apps, Firebase Auth's SDKs have been battle-tested by millions of applications.

Supabase Auth supports a broad range of OAuth providers (over 20, including GitHub, GitLab, Bitbucket, Notion, Spotify, and more) through a unified configuration. Firebase Auth supports social login primarily through OAuth/OIDC configuration, with first-class support for Google, Apple, GitHub, and a few others, but adding custom OAuth providers requires more manual work.

Performance & Scale

Supabase's free tier allows 50,000 MAU, which is generous. The managed cloud service scales automatically, and self-hosted deployments can be sized to any scale. Firebase Auth scales with Google's infrastructure and has no practical limits for consumer apps. Both are reliable for production use at scale; the difference in performance characteristics is negligible for the vast majority of applications.

When to Choose Each

Choose Supabase Auth if you are building on Supabase's stack — the Postgres RLS integration alone justifies it, and data portability means you are never locked into a vendor. It is also the right choice if you have self-hosting requirements or want to audit the auth codebase.

Choose Firebase Auth if your app is mobile-first and you want the most polished native SDKs, or if you are already using Firestore and want your security rules tied to Firebase Auth identities. Phone number authentication at scale is also a Firebase strength.

Bottom Line

Supabase Auth is the better choice for PostgreSQL-centric applications and teams that value open source and portability. Firebase Auth is the stronger choice for mobile-first apps and teams already committed to the Firebase/Google ecosystem.