Introduction

What is Supabase?

Supabase is an open-source backend-as-a-service (BaaS) that positions itself as a Firebase alternative. Unlike Firebase which uses NoSQL document stores, Supabase is built on PostgreSQL — one of the most powerful and battle-tested relational databases in the world. It gives you a full PostgreSQL database, an auto-generated REST API, realtime subscriptions, authentication, and file storage out of the box.

Because Supabase is open-source, you can self-host it on your own infrastructure or use the managed cloud offering at supabase.com. The project started in 2020 and has grown rapidly, becoming the go-to backend for developers who want the convenience of a BaaS without sacrificing the power of SQL.

How Supabase Works

Every Supabase project is a dedicated PostgreSQL database instance. When you define tables, Supabase automatically generates a REST API using PostgREST, a realtime API using the Realtime engine, and integrates authentication via GoTrue. This means you don't write backend code for basic CRUD operations — the APIs are generated for you.

The workflow is straightforward: define your database schema with SQL or the Table Editor, then use the Supabase client library in your frontend to read and write data. The same database handles your relational data, user sessions, file metadata, and realtime subscriptions.

Supabase vs Firebase

Feature	Supabase	Firebase
Database Type	PostgreSQL (relational)	Firestore / Realtime DB (NoSQL)
Query Language	SQL + REST API	SDK methods only
Open Source	Yes (MIT license)	No (proprietary)
Self-Hostable	Yes	No
Realtime	WebSocket-based	SDK-based
Auth Providers	50+ (GoTrue)	10+ (Firebase Auth)
File Storage	S3-compatible	Google Cloud Storage
Free Tier	500MB DB, 50MB storage	1GB Firestore, 5GB storage

Architecture Overview

Supabase is a collection of open-source tools working together:

PostgreSQL — The core database engine. All data is stored in PostgreSQL tables with full relational integrity, indexes, views, triggers, and functions.
GoTrue — A SWT-based authentication server that handles user sign-up, sign-in, session management, and social logins. It stores users in the auth schema of your PostgreSQL database.
PostgREST — Turns your PostgreSQL database into a RESTful API. It reads your table schemas and generates endpoints automatically, including support for filtering, sorting, and pagination.
Realtime Engine — Listens to PostgreSQL replication slots and broadcasts changes over WebSockets. Clients can subscribe to insert, update, delete, or row-level changes in real time.
Storage — An S3-compatible file storage layer with its own REST API. Files are stored in buckets, and access is controlled through RLS policies just like your database tables.

Key Features

Auto-generated APIs — Define a table and instantly get REST and GraphQL endpoints without writing a single line of backend code.
Realtime Subscriptions — Subscribe to database changes with a single line of JavaScript. Changes propagate instantly to all connected clients.
Built-in Auth — Email/password, OAuth (Google, GitHub, etc.), magic link, and phone auth. Session handling and token refresh are automatic.
File Storage — Upload, serve, and organize files with the same RLS policies you write for database tables.
100% PostgreSQL — You get full SQL access. Use joins, window functions, CTEs, triggers, and extensions like PostGIS.

PostgreSQL at the Core
PostgreSQL is the backbone of Supabase. Unlike Firebase's NoSQL model, PostgreSQL gives you relational integrity, powerful querying with SQL, and a mature ecosystem of extensions. If you already know SQL, you already know how to work with Supabase. If you don't, learning SQL is one of the best investments you can make as a developer — it transfers across every relational database.

When to Use Supabase

Supabase is a great fit when you need a relational data model, want full control over your backend, or prefer open-source tools. It shines in projects that require complex queries, joins, or transactional integrity — things that are awkward in NoSQL databases. It is also ideal if you want to avoid vendor lock-in since you can export your PostgreSQL database at any time.

Use Supabase for new projects where you want to move fast without writing a dedicated backend. It also works well as a companion to existing PostgreSQL databases, providing an instant API layer on top of your existing data.

Client Initialization

import { createClient } from '@supabase/supabase-js'

const supabaseUrl = 'https://your-project.supabase.co'
const supabaseAnonKey = 'your-anon-key-here'

const supabase = createClient(supabaseUrl, supabaseAnonKey)

The createClient function takes your project URL and anon key, both found in the API settings of your Supabase dashboard. This single client handles database queries, realtime subscriptions, auth, and storage operations throughout your application.

Exercise
Create a new HTML file and initialize the Supabase client with your project URL and anon key. Use a script tag with the CDN import instead of the npm module. Log the client object to the console to confirm it loads correctly.