Two Philosophies

Supabase and Firebase solve the same problem — giving developers a managed backend so they can ship faster — but they approach it from fundamentally different directions. Firebase is a Google product built on proprietary infrastructure with NoSQL (Firestore) at its core. Supabase is an open-source project built on Postgres with a philosophy of using existing, proven technologies rather than inventing new ones.

This philosophical difference affects everything: data modeling, querying, vendor lock-in, pricing, and the day-to-day experience of building with each platform.

We built a task management application (think a simplified Linear) on both platforms over three weeks. The app includes user authentication, a relational data model with projects, tasks, and comments, file attachments, real-time updates, and role-based access control. These features exercise every major capability of both platforms.

Database

This is the most consequential difference between the two platforms.

Supabase gives you a full Postgres database. You write SQL. You define schemas with foreign keys, indexes, views, and stored procedures. If you know Postgres, you know how to use Supabase's database. The learning curve is the learning curve of SQL itself.

Firebase's Firestore is a document database. Data is stored in collections of documents, each document a JSON-like object. There are no joins. Relationships are modeled through subcollections or document references. Queries are limited compared to SQL — you cannot, for example, filter on two inequality conditions on different fields.

-- Supabase: Get all tasks for a project with assignee details
SELECT
  t.id, t.title, t.status, t.priority,
  u.name AS assignee_name, u.avatar_url
FROM tasks t
LEFT JOIN users u ON t.assignee_id = u.id
WHERE t.project_id = 'proj_123'
ORDER BY t.priority DESC, t.created_at DESC;
// Firebase: Same query requires multiple reads
const tasksSnap = await getDocs(
  query(
    collection(db, 'projects', 'proj_123', 'tasks'),
    orderBy('priority', 'desc')
  )
);
// Now fetch each assignee separately...
const tasks = await Promise.all(
  tasksSnap.docs.map(async (doc) => {
    const data = doc.data();
    const userSnap = await getDoc(
      doc(db, 'users', data.assigneeId)
    );
    return { ...data, assignee: userSnap.data() };
  })
);

For our task management app, the relational nature of the data made Supabase the natural fit. Projects have many tasks, tasks have many comments, users can be assigned to multiple tasks across projects. In Postgres, these relationships are expressed directly. In Firestore, we spent considerable time deciding on data denormalization strategies.

That said, Firestore has genuine strengths. Its offline persistence works out of the box — the SDK caches data locally and syncs when connectivity returns. For mobile applications with intermittent connectivity, this is valuable. Supabase's real-time features require an active connection.

Authentication

Both platforms offer solid authentication with email/password, OAuth providers, and magic links.

FeatureSupabase AuthFirebase Auth
Email/passwordYesYes
OAuth (Google, GitHub, etc.)Yes (20+ providers)Yes (15+ providers)
Magic linksYesYes
Phone/SMSYesYes
Anonymous authYesYes
Multi-factor authYesYes
Custom claimsVia JWT / RLSYes (Admin SDK)
Self-hostableYesNo

In practice, both auth systems work well. Supabase's auth integrates tightly with Postgres Row Level Security (RLS), which means your access control is defined at the database level. Firebase uses Security Rules, a custom DSL that sits in front of Firestore. Both approaches have tradeoffs — RLS is more powerful but requires SQL knowledge; Security Rules are more approachable but less expressive.

We found Supabase's RLS policies easier to reason about for complex access control. Our task app required rules like "team leads can reassign any task in their project, but members can only modify tasks assigned to them." In Supabase, this was a SQL policy. In Firebase, the equivalent Security Rule was verbose and harder to test.