I've shipped projects on both Supabase and Firebase. Here's my honest breakdown after using them in production.
Supabase: The SQL Option
Supabase is Postgres under the hood. If you know SQL, you'll feel at home. Row-level security is powerful once you understand it, and the realtime subscriptions work great. The dashboard is clean and the docs are excellent.
I use Supabase for most of my projects because I prefer relational data and the ability to write raw SQL when I need to.
Firebase: The NoSQL Option
Firebase is mature, battle-tested, and has features Supabase is still building — like Firebase Auth's phone authentication and Firebase ML. Firestore's document model is intuitive for simple apps.
The downside is vendor lock-in. Once you're deep in Firebase, moving off it is painful.
My Recommendation
For new projects in 2026, I default to Supabase. Open source, SQL-based, generous free tier, and the ecosystem is growing fast. But Firebase is still the right choice if you need specific features it offers.