Both Supabase and Firebase let you ship a working product without building a backend from scratch. Both have generous free tiers. So the question isn't "which is better" — it's "which fits this MVP." Here's how I decide.
The one difference that drives everything: the data model
Firebase (Firestore) is a NoSQL document store — you think in collections and documents. Great for fast writes, real-time updates, and naturally nested data. Supabase is Postgres — a real relational database. You think in tables, rows, and relationships, and you can write SQL.
Everything else flows from this. If your data has clear relationships (users have orders, orders have items), Postgres keeps your data honest with constraints and joins. If your data is loose and document-shaped, Firestore fits comfortably.
Auth, storage, and the "batteries included" parts
Both give you authentication, file storage, and serverless functions out of the box, so neither blocks you on day one. Firebase auth is extremely mature and plugs into the Google ecosystem. Supabase auth is built on Postgres with Row Level Security, so your access rules live next to your data as policies. For an MVP both are more than enough — auth is rarely the deciding factor.
Pricing shape (not exact numbers — those change)
Don't compare sticker prices; compare the shape of how you pay. Firestore bills heavily by reads, writes, and deletes — apps that read the same data a lot can see costs climb in surprising ways at scale. Supabase bills more like traditional hosting (compute, storage, bandwidth), which is easier to predict. For an early MVP both are cheap or free; the shape matters most as you grow.
Vendor lock-in
This is where I lean Supabase for most clients. Because it's Postgres underneath, you can take your database and leave — export it, self-host it, or move to any Postgres provider. Firestore's data model is proprietary; migrating off it later is real work. If owning your data matters, that's a strong point for Supabase.
Real-time and offline
Firebase has best-in-class offline support and real-time sync — if you're building a mobile app that must work on a subway, that's a genuine edge. Supabase has real-time subscriptions too, and they're good, but Firebase's offline story for mobile is still ahead.
My rule of thumb
Pick Supabase if: your data is relational, you value SQL and predictable pricing, you want to avoid lock-in, or your team knows Postgres. This covers most web SaaS MVPs. Pick Firebase if: you're building mobile-first with heavy offline needs, your data is document-shaped, or you're already deep in Google's ecosystem.
Either way, the worst choice is agonising over it. Both will get your MVP in front of users this month — the only thing that matters at the MVP stage.
Deciding on a stack, or want your MVP built fast and clean on Next.js + Supabase? I help founders ship a real product instead of a prototype — vengstudio.online.
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