Supabase and Firebase are both backend-as-a-service platforms that let you build without managing infrastructure. They cover the same surface area — auth, database, storage, real-time subscriptions, serverless functions — but with fundamentally different data models and cost structures.
Firebase Firestore is a document database optimized for mobile and real-time sync. Data is organized as collections of documents, and the real-time listener API lets clients receive updates in milliseconds. This makes Firebase excellent for chat applications, collaborative tools, and any product where live data sync across clients is a core feature. The Firebase SDK (especially on iOS and Android) is deeply mature. Authentication supports 12 providers out of the box. Cloud Functions extend the backend. The downside: Firestore's query model is restrictive — no full-text search, no aggregate queries across collections, no multi-collection joins. And the pricing structure charges per read/write operation, which can surprise teams — 1M document reads costs $0.06, but a dashboard page that reads 500 documents per visit at 10,000 daily active users = $30/day in reads alone.
Supabase is PostgreSQL with a REST/realtime API layer, auth, storage, and edge functions. You get the full power of SQL — joins, aggregations, full-text search, custom functions, triggers, row-level security. The real-time system uses PostgreSQL logical replication to stream changes, so you can subscribe to any SQL query result as a live stream. The free tier includes 500MB database, 1GB file storage, and 50K monthly active users for auth. Paid plans start at $25/month. Pricing is predictable because it's based on compute and storage, not per-operation.
The migration story matters: Firebase lock-in is real. The Firebase SDK has deep platform integration, and migrating off requires rewriting data access logic. Supabase uses PostgreSQL, which you can export and run anywhere.
Practical guidance: Firebase for mobile-first, real-time collaborative applications where the client SDK experience is paramount. Supabase for web applications, relational data requirements, teams with SQL experience, or anyone concerned about predictable pricing at scale.