Backend as a Service gives you auth, a database, storage and realtime APIs out of the box — so a frontend can ship a full product without a custom backend.
Backend as a Service collapses the typical backend stack — authentication, a database, file storage, access control and realtime updates — into a single managed product your frontend can call directly. For solo developers and small teams, that is transformative: you skip building login, REST endpoints and a storage layer, and spend your time on the actual product. Supabase and Firebase are the leading choices, one built on Postgres, the other on a document model.
The categories’ superpower is also its main caveat. Because the client talks to the backend directly using a public key, the access rules you write — Supabase’s Row Level Security or Firebase’s Security Rules — are what actually protect your data. Treat those policies as core application code, not an afterthought, because they are the security boundary that stands between a user and everyone else’s rows.
Free tiers here are multi-dimensional, so compare carefully. Look at database size, the number of monthly active users included for auth, file storage and bandwidth, and how much server-side logic (edge functions, triggers) you can run. Also check whether free projects pause after a period of inactivity, since that affects anything users expect to be always available. The best fit depends on whether you prefer Postgres and SQL (Supabase) or a realtime document store with deep Google integration (Firebase).
Firebase Google Firebase is Google's mobile and web application development platform that helps you build, improve, and grow your app.
Free tier
Spark includes 1 GiB Firestore and 10 GB Hosting; Cloud Storage and Cloud Functions require Blaze billing
Pay-as-you-go · Multi-region
Supabase NEW Supabase Inc. Supabase is an open source Firebase alternative with Postgres, Auth, instant APIs, Edge Functions and Realtime subscriptions.
Free tier
500 MB database, 1 GB file storage, 5 GB egress plus 5 GB cached egress
Paid from $25/mo · Multi-region
Pauses when idle · Suspends at the limit
Use a BaaS when you want to move fast and the provider's auth, database and storage cover your needs — it removes weeks of boilerplate. Build your own when you have unusual requirements, want full control of the data layer, or need to avoid vendor lock-in.
A database stores data; a BaaS wraps a database with authentication, file storage, access-control rules, auto-generated APIs and often realtime updates. You get a working backend, not just a place to put rows.
It can be, but security depends entirely on access rules — Row Level Security in Supabase, Security Rules in Firebase. Those policies, not your client code, are the real boundary, so getting them right is essential.