Supabase vs Firebase (2026): Which Backend to Build Your AI App On

Pick Supabase if your app is data-heavy, you want SQL, and you ever plan to leave; pick Firebase if you are shipping a real-time mobile app and want zero billing setup on day one. The rest is the cost math and the two walls each one hits.

Both are a "backend-as-a-service," meaning the database, auth, file storage, and API are handled for you so you never stand up a server. That is where the similarity ends. They store data in fundamentally different shapes, they bill on opposite models, and one of them you can walk away from while the other you mostly cannot. For an AI app in 2026, those three differences decide more than any feature checkbox.

Here is the short version, then the math that backs it.

The verdict, by what you are building

If your app is mostly tables that relate to each other (users, orders, posts, comments) and you can write or read SQL, build on Supabase. You get a real PostgreSQL database, which means joins, transactions, and a schema that stops bad data at the door. It is also open source, so the day you outgrow the hosted plan you can take the whole database and run it anywhere. That exit door is worth more than most founders realize until they need it.

If your app's core feature is live, synced state across devices (a chat app, a collaborative tool, anything that has to feel instant offline), build on Firebase. Firestore's real-time sync and offline persistence are still the gold standard, and you can ship without even entering a credit card. The tradeoff is that you are renting from Google on Google's terms, and the bill is metered per operation, which is exactly where teams get surprised.

Everything below is how those two calls hold up under real pricing, real AI features, and the gotchas that decide it once you are in production.

The one axis that actually decides it

Strip away the feature lists and one question separates these two: do you own a database you can leave, or do you rent a service you cannot?

Supabase is PostgreSQL with a dashboard on top. PostgreSQL is the most widely deployed open-source relational database on earth, and Supabase does not fork it or hide it. You get the raw connection string. If you ever want to migrate to your own server, to AWS, to a different host, you run a standard pg_dump and you are gone. Nothing is proprietary about your data.

Firebase is Firestore, a NoSQL document database that exists only inside Google. NoSQL means there is no fixed schema: you store JSON-like documents and the database does not force relationships between them. That makes early prototyping fast, because you never stop to design tables. It also means there is no SQL, no real joins, and no clean way to export your data into another system later. The data model and the vendor are the same decision. You cannot take Firestore with you.

For most AI apps the answer leans Supabase, because AI features lean on structured, queryable data: a users table, a documents table, an embeddings column you can filter and join. NoSQL can do this, but you end up rebuilding in your application code what SQL gives you for free. The exception is when "instant sync across devices" is the actual product, which is the one thing Firestore does better than anyone.

:::callout{variant="note" title="What "relational" buys you in practice"}
Say a user deletes their account and you need every comment, like, and file they ever created to go with it. In PostgreSQL that is one rule defined once (a foreign key with cascade delete) and the database enforces it forever. In Firestore you write code to find and delete each related document yourself, and if you miss a path, orphaned data piles up. Relational databases make "data that belongs together stays consistent" the database's job instead of yours.
:::

Pricing, the part everyone gets wrong

The headline is not the monthly price. It is the billing model. Supabase charges a flat tier plus predictable overage; Firebase charges per operation, so your bill moves with your traffic, sometimes overnight.

Supabase: a flat number you can plan around

Supabase Free is $0 and covers a real app: 50,000 monthly active users, a 500 MB database, 5 GB egress, and 1 GB of file storage. The catch that bites everyone: free projects pause after one week of inactivity, and you are limited to 2 active projects. A paused project means your demo is down until you click to restore it, which is fine for a side project and a problem for anything a client might open unannounced.

Supabase Pro is $25/month, first project included, additional projects from $10/month. That $25 buys 100,000 MAU (then $0.00325 per extra MAU), 8 GB of disk per project (then $0.125/GB), 250 GB of egress (then $0.09/GB), and 100 GB of file storage (then $0.0213/GB). It also includes $10/month in compute credits, enough to run one small always-on instance. The Team plan jumps to $599/month and mostly adds compliance (SOC2, ISO, SSO); below that you do not need it.

The reason builders like this model: you can look at your user count and know your bill. Pro at $25 covers a real production app, and the overage rates are low enough that 10,000 active users with a few gigabytes of data still lands in the $25 to $50 range.

Firebase: free until it is not, then metered

Firebase Spark is the genuinely free plan, and its best trait is that it needs no payment method at all. You get Firestore with 1 GiB stored, 50K reads/day, 20K writes/day, 20K deletes/day, and 10 GiB/month of egress; Authentication for 50K monthly active users; and Realtime Database with 1 GB stored and 10 GB/month download. For a prototype or a low-traffic app, you can sit on Spark indefinitely and pay nothing, no card on file.

The moment you need more, you switch to Blaze, the pay-as-you-go plan (Google gives $300 in free credit if you are eligible). Blaze keeps the Spark free limits, then meters everything past them: Cloud Functions are 2M invocations/month free then $0.40/million; Cloud Storage is $0.026/GB stored after 5 GB and $0.12/GB downloaded after 1 GB/day; Firestore reads, writes, and deletes past the daily free tier bill per operation through Google Cloud pricing. Firebase now also offers managed PostgreSQL through SQL Connect, a 3-month free trial then starting around $9.37/month, a quiet admission that a lot of people want SQL after all.

Free tier face-off

Both give you 50,000 monthly active users free, which is more than enough to validate almost anything. The difference is in the two catches.

Supabase's catch is the pause: leave a free project idle for a week and it goes to sleep until you wake it. Annoying for demos, irrelevant once you have real traffic or you are on Pro.

Firebase's catch is the upgrade cliff: Spark is truly free with no card, but the instant you outgrow it you are on metered billing, and metered billing is unpredictable by design. There is no $25 "just give me a bit more for a flat price" tier. You go from free to pay-per-use in one step.

So the honest free-tier read: Firebase wins for a zero-commitment prototype you might never charge for, because no card and no pause. Supabase wins the moment the project is real, because $25 flat beats "we will meter you and see."

Building an AI app on each

This is where 2026 actually differs from 2022, and where Supabase pulls ahead for most builders. An AI app usually needs to store embeddings (the numerical fingerprints of your text) and find the closest matches to a query. That is vector search, and it is the engine behind retrieval, semantic search, and RAG (retrieval-augmented generation, where you feed an LLM your own documents).

Supabase ships this natively through pgvector, a PostgreSQL extension that stores and indexes vectors right next to your normal data. Because it is one database, you can run a single query that filters by a user's ID and ranks by vector similarity at the same time. No second system, no syncing. Supabase's AI toolkit also wires straight into OpenAI and Hugging Face embeddings.

Firebase answers with Firestore vector search through the findNearest query, so you can store embeddings on a document and retrieve nearest neighbors without leaving Firestore. It works, and if you are already deep in Firestore it saves you a second database. But you are doing vector math in a document store that was not designed around it, and you lose the SQL filtering that makes pgvector queries so clean. For an AI-first app, pgvector is the more natural home.

1. 1

   Storing an embedding on Supabase

   Enable the extension with create extension vector;, add a column like embedding vector(1536) to your table, then insert the embedding array alongside the row's normal data. One table holds your content and its vector.

2. 2

   Querying for the closest matches

   Run an ordinary select ordered by the vector distance operator (embedding <=> query_embedding) with a limit. You can add a normal where user_id = ... in the same query, so similarity search and access control happen in one round trip.

3. 3

   Indexing so it stays fast

   Add an HNSW index on the vector column. This keeps nearest-neighbor lookups fast as the table grows, the same way a normal index speeds up a normal column.

Auth, real-time, and the rest

Both cover authentication well. Firebase Auth is the more mature, with a long list of providers and the smoothest mobile SDKs; if "let users sign in" needs to just work on iOS and Android, it is excellent. Supabase Auth is built on your Postgres database and pairs with RLS (row-level security, meaning each user can only read or write their own rows, enforced by the database itself). RLS is the single most important Supabase concept to learn, because it is what makes a multi-user app safe without you writing permission checks in every API call.

Real-time is Firebase's home turf. Firestore and the Realtime Database sync state across devices and handle offline gracefully, queuing writes and replaying them when the connection returns. Supabase has Realtime too, built on Postgres's change feed, and it is good for live dashboards and presence, but it is not the offline-first experience Firebase mobile apps lean on. If your product is a collaborative or offline-heavy mobile app, weight this heavily toward Firebase.

The decision rule, by who you are

Which is better, Supabase or Firebase?

Neither universally. Supabase is better for data-heavy apps that want SQL, AI features, and the freedom to migrate later. Firebase is better for real-time, offline-first mobile apps and for zero-commitment prototypes that need no credit card. Match the tool to whether your core feature is structured data or live sync.

Why is Google shutting down Firebase?

Google is not shutting down Firebase. The confusion comes from specific legacy products being deprecated (for example, Firebase Dynamic Links shut down in August 2025) and from Google folding some features into Google Cloud. The core platform is actively developed, with newer additions like Firebase Studio, AI Logic, and managed PostgreSQL through SQL Connect.

Is Supabase part of Firebase?

No. Supabase is a separate, independent company, often described as the open-source Firebase alternative. It gives you the same kind of all-in-one backend (database, auth, storage, APIs) but built on PostgreSQL instead of Google's proprietary Firestore.

What are the downsides of Supabase?

Two main ones. Free projects pause after a week of inactivity, which interrupts demos. And its real-time and offline-sync experience, while solid, is less mature than Firebase's, so for offline-heavy mobile apps Firebase still has the edge. You also need to learn RLS to keep multi-user apps secure.

Is Supabase or Firebase cheaper?

For a true zero-traffic prototype, Firebase Spark is cheaper because it is free with no card. Once you have real usage, Supabase is usually cheaper and far more predictable: a flat $25/month Pro plan versus Firebase's per-operation metered billing that rises with traffic. The more your app reads and writes, the more Supabase's flat model tends to win.

Pick your backend, then make the rest of the stack match it. I send one builder teardown like this each week, the real costs and the walls included. Get it in your inbox.