Supabase vs Firebase in 2026: which backend for a web app?

For most web apps with users, accounts and related data (SaaS, internal tools, client portals), Supabase is the better default: its PostgreSQL database handles relations, filters and reporting with plain SQL. Firebase is the better choice when your app is built around realtime sync, offline use on mobile, or you already live in Google Cloud. Both have a free tier and both scale; the difference is the data model, and it is hard to change later.

This guide compares them on the points that matter for a small team or an app generated by AI: data model, queries, authentication, security rules, storage and functions, free tiers, pricing, and lock-in. Plan details were checked in November 2026 on the vendors' pricing pages; they change, so confirm before you commit.

The short answer, in one table

Supabase is a PostgreSQL backend with auth, storage and functions; Firebase is a Google backend built around the Firestore document database. The table gives the contrast line by line.

Data model: tables or documents

Supabase stores data in related tables; Firestore stores it as documents grouped in collections. The choice shapes everything after it.

A business app is full of relations: a client has projects, a project has tasks, a task has comments, an invoice belongs to a client. In PostgreSQL you declare those links with foreign keys and the database enforces them. In Firestore you decide for each screen whether to nest data inside a document or to duplicate it, and you keep the copies in sync yourself. Duplication makes reads fast and simple, but every change to a client name then has to touch many documents.

Firebase now also offers a relational option: its documentation describes a managed PostgreSQL database on Cloud SQL, exposed through the Firebase SDKs. It is a separate product from Firestore, so check which one a tutorial or an AI-generated project actually uses.

Queries and reporting

If you will ever ask "how many orders per client per month", you want SQL. In Supabase you write that as one query with a join and a group by, or you give the question to a spreadsheet or BI tool that connects to Postgres directly.

Firestore is built for fetching documents by path or by simple filters, which is fast and cheap at any size. It is not designed for ad hoc aggregation across collections. Teams usually add counters maintained by functions, or export the data to another system for analytics. For a dashboard-heavy internal tool this extra work is real; for a chat or a feed it rarely matters. Our guide on how to build internal tools shows why reporting often ends up being the main feature.

Authentication

Both services ship ready-made authentication with email, OAuth providers and per-user sessions, and both list 50,000 monthly active users on their free plans. For a typical web app, auth is not the deciding factor.

Two differences are worth knowing. In Supabase, users live in your Postgres database, so you can join them to your own tables. On Firebase, phone sign-in is not available on the free Spark plan and is billed per SMS on Blaze. If your users sign in with a phone number, check that line first. For a deeper look at the Supabase side, see our guide on Supabase Auth.

Security: RLS versus Security Rules

Both systems let the browser talk to the database directly, so both depend on server-side rules to keep one user away from another user's data. The rules are not optional.

Supabase uses PostgreSQL row level security. A policy attached to a table acts like an extra WHERE clause on every query, for example "a user can read rows where user_id equals their own id". According to the Supabase documentation, RLS is not on by default: you enable it per table, and the service role key bypasses it, so it must stay on the server. A table without RLS and with default grants can be readable by anyone holding the public key, which is the most common mistake in generated apps.

Firebase uses Security Rules, a separate language of match and allow statements checked against every client request. Server libraries bypass them and are governed by Google Cloud IAM instead. Firebase documents a simple "allow everything" rule and warns never to use it in production; leaving it in place is the Firebase version of the same mistake.

One practical edge for Supabase: policies are plain SQL, and AI models write SQL well. The Firebase rule language is smaller and less represented in training data. This is an observation about tooling, not a guarantee in either direction.

Storage and server functions

Both offer file storage and server functions; the main difference is what the free plan includes. Supabase Storage is part of the Free plan (1 GB). On Firebase, the Spark plan marks Cloud Storage and Cloud Functions as not available, so a web app that needs uploads or a server-side secret has to move to Blaze.

You need server functions as soon as you call a service with a secret key: payments, email, an AI model. Supabase calls them Edge Functions, with 500,000 invocations on Free and 2 million on Pro. Cloud Functions for Firebase run JavaScript, TypeScript or Python and can be triggered by Firestore, Auth or Storage events, by HTTPS calls or by a schedule, with 2 million invocations a month free on Blaze. Firebase has the richer set of event triggers; Supabase has the simpler mental model.

Free tiers and what paid costs

Supabase charges a predictable monthly plan; Firebase charges for usage, so its bill follows traffic. Figures below were checked in November 2026 on supabase.com/pricing and firebase.google.com/pricing.

Two consequences. First, Supabase Free pauses a project after a week without activity, which is fine for a prototype and wrong for a live product, so real apps go to Pro. Second, Firestore bills per document read and write: a screen that loads 200 documents costs 200 reads each time, and a bug that loops a query can produce a large bill on Blaze. Supabase's model is closer to a flat rate with usage limits. Pro includes limits (for example 250 GB egress) beyond which extra usage is charged; read the pricing page for the current overage rates.

Lock-in and self-hosting

Supabase can be self-hosted and is built on standard PostgreSQL, so leaving costs you a database dump; leaving Firebase means rewriting your data layer. Supabase documents a Docker-based self-hosting path. Even if you never self-host, your data sits in a Postgres database that any host can run.

Firebase is a Google service with its own SDKs, query model and rules language. Moving off Firestore means redesigning the schema into tables and rewriting every query. That is a normal price for a managed product, and Google's infrastructure is a real strength, but you should count it. Lock-in also depends on who owns the project: our article on Supabase as a backend for AI builders explains the bring-your-own versus platform-managed question.

Why AI app builders mostly pick Supabase

AI builders favour Supabase because a language model can write SQL schemas and policies, and a developer can open the result later in a standard tool. That is a reasoned guess about incentives, not a vendor statement. What is documented: Lovable's built-in backend is based on Supabase's open-source foundation, and Lovable also lets you connect a Supabase project you own.

Cadrant, our builder, also uses Supabase: it generates React web apps on a Supabase project in your own account, with the AI writing the migrations and the RLS policies. We chose it for the reasons above, and it comes with a cost we accept: you work with SQL concepts and with a Supabase bill separate from ours. If your team is already deep in Firebase, or you need offline-first mobile sync, an AI builder on Supabase will not serve you better. Compare tools in our best AI app builders guide, and see our Supabase connection docs for how the link works.

Which one for which case

Choose by the shape of your data and your exit plan, not by the logo.

If you are still choosing a tool to build the app itself, the Cadrant web app builder page shows what the AI generates on a Supabase backend.