Guides / Comparisons

Supabase vs Firebase: Which Backend Should You Pick?

Supabase vs Firebase compared: Postgres vs NoSQL, free tier limits, pricing, auth, functions and lock-in as of September 2026, and who each backend suits.

Mythex Team · 2026-09-29 · 6 min read

Pick Supabase if your data is relational (customers, orders, invoices that link to each other), you want to write SQL, or you want an open-source stack you could self-host later. Pick Firebase if you're building a mobile-first app that needs offline sync and realtime updates out of the box, or you're already on Google Cloud. Both give you a database, login, file storage and serverless functions. The real choice is Postgres (SQL) vs Firestore (NoSQL), and how each one bills you.

Supabase vs Firebase at a glance

MAU means monthly active users: people who signed in during the month. Check Supabase pricing and Firebase pricing for the current numbers.

How we compared

We compared the publicly stated features, quotas and prices on Supabase's and Firebase's own websites and documentation as of September 2026. We did not do hands-on testing or benchmark performance, and we left out anything we couldn't confirm on the vendors' pages. Prices are in US dollars and exclude tax.

The real difference: Postgres vs Firestore

This one decision shapes everything else.

Supabase is built on Postgres, a relational database: data lives in tables with rows and columns, and tables link to each other. You query it with SQL, and Supabase generates an API from your tables automatically. If your app has a customer who has orders, and each order has line items, that fits tables naturally. Our guide to what Postgres is explains it in plain terms.

Firestore is a NoSQL document database. Data lives in documents (similar to JSON objects) grouped into collections. Google describes it as a flexible, scalable database that apps access directly with native SDKs, with realtime sync and offline caching for data the app is using. That makes it quick to start and strong on phones with patchy connections. Complex reporting across many related records is harder than in SQL.

Firebase now also offers SQL Connect, which gives you Cloud SQL for PostgreSQL through Firebase. As of September 2026, Firebase lists a three-month no-cost trial for the first instance, then a monthly charge. So "Firebase can't do SQL" is no longer true, but Postgres is an add-on there, not the centre.

If you're unsure which shape your data has, read SQL vs NoSQL first.

Free plans compared

Supabase Free (as of September 2026):

• 500 MB database on a shared CPU with 500 MB RAM
• 50,000 monthly active users
• 1 GB file storage and 5 GB egress (data sent out)
• 500,000 Edge Function invocations
• A limit of 2 active projects
• Projects are paused after 1 week of inactivity
• No backups; logs kept for about a day

Firebase Spark (as of September 2026), no payment method needed:

• Cloud Firestore: 1 GiB stored, 50K reads, 20K writes and 20K deletes per day
• Authentication: 50K monthly active users
• Hosting: 10 GB storage and 360 MB/day transfer
• Realtime Database: 1 GB stored, 100 simultaneous connections
• Cloud Functions, App Hosting and new Cloud Storage buckets are not available on Spark

The practical difference: Supabase's free plan includes serverless functions but pauses quiet projects. Firebase's pricing page doesn't mention pausing idle Spark projects, but you need to move to Blaze (with a billing account) for server-side code and new storage buckets.

Paid pricing compared

Supabase charges a monthly plan fee plus usage above the included quotas:

• Pro, from $25/month: 8 GB disk per project, 100,000 MAUs, 250 GB egress, 100 GB file storage, 2 million Edge Function invocations, $10/month in compute credits, daily backups kept 7 days. Overage examples: $0.125 per extra GB of disk, $0.09 per extra GB of egress.
• Team, from $599/month: same included usage, plus 14-day backups and 28-day log retention.
• Enterprise: custom.

Firebase Blaze is pay as you go and needs an active billing account. You get the no-cost quotas first, then pay per use at Google Cloud rates. Cloud Functions, for example, are no-cost up to 2 million invocations a month, then $0.40 per million. Eligible new users can get $300 in Google Cloud credit.

Which is cheaper depends on your app. A flat $25 is easy to budget. Pay-per-read can be very cheap for a small app, but a Firestore app that reads a lot of documents on every screen can grow its bill quickly. Estimate both before you commit.

Auth, storage and functions

• Auth: both include hosted sign-in, and both give 50K monthly active users free. Supabase pairs auth with Postgres Row Level Security, rules in the database that decide which rows each user can see. Firebase counts SAML/OIDC (enterprise single sign-on) users separately, with 50 free. For the basics, see what authentication is.
• Storage: Supabase Storage is S3-compatible with a CDN and image transformations. Firebase Cloud Storage for new buckets needs Blaze.
• Functions: Supabase Edge Functions run TypeScript on Deno. Firebase Cloud Functions need Blaze.
• AI: Supabase offers Vector, built on pgvector, for embeddings. Firebase offers AI Logic, billed at Google Cloud or Gemini API rates, and Firebase Studio.

Lock-in and portability

Supabase says all its core tools are open source and self-hostable, and because the database is standard Postgres you can dump it and load it into any Postgres host. That's the strongest argument for Supabase if you worry about being tied to one vendor.

Firebase is a managed Google service. You can export your data, but Firestore's document model and security rules are specific to Firebase, so moving elsewhere means redesigning the data and rewriting the code that uses it.

Who each one suits

Choose Supabase if:

• Your data is relational: users, teams, orders, invoices, bookings
• You or your developer like SQL, or want reporting and dashboards
• You want the option to self-host or move to another Postgres host
• A predictable monthly fee suits your budget

Choose Firebase if:

• You're building a mobile app that must work offline and sync later
• You want realtime listeners with very little setup
• You already use Google Cloud, Google Analytics or other Firebase tools
• Your data really is document-shaped and you'd rather pay per use

Where Mythex fits

Supabase and Firebase are backends: you still build the app on top of them and host the frontend somewhere. If you'd rather describe the app in chat and get the whole thing, Mythex is an AI app builder that writes the code, runs it in a live preview and publishes it. When your app needs to store data, Mythex adds a dedicated Postgres database for that project, which sleeps after 5 idle minutes and bills from the same credit balance as building and hosting.

That's a good fit for web apps like a client portal, CRM or booking tool. It isn't a replacement for Firebase's offline mobile sync, and Mythex doesn't build native App Store apps yet. If you already use Supabase or Firebase, you can also ask the Mythex agent to connect to your existing project using your own keys. See how to add a database to your app for the general approach.

Verdict

• Supabase is the stronger default for web apps and SaaS products with relational data, and for anyone who values SQL and portability.
• Firebase is the stronger pick for mobile-first apps that need offline sync and realtime updates, and for teams already invested in Google Cloud.

Both have generous free plans, so the cheapest way to decide is to build one small feature on each and see which feels natural. For more backend options, see our Supabase alternatives roundup.