Best Open Source Backend-as-a-Service Platforms in 2026

TL;DR

Firebase's Blaze plan charges per read, write, and function invocation — a production app at 100K MAU often exceeds $200–500/month. Supabase is the best Firebase replacement: PostgreSQL-backed, full-featured, with an excellent developer experience. PocketBase delivers 80% of Supabase's capabilities in a single 5 MB Go binary — ideal for MVPs and side projects. Appwrite has the best multi-platform SDK coverage for apps targeting web and mobile simultaneously.

Key Takeaways

• Supabase (Apache-2.0, 73K+ stars) is a full Firebase replacement built on PostgreSQL — the most widely adopted open source BaaS
• Appwrite (BSD-3, 45K+ stars) has official SDKs for 10+ platforms including Flutter, React Native, and Apple platforms — best for cross-platform development
• PocketBase (MIT, 41K+ stars) runs as a single Go binary on 128 MB RAM — the fastest path from idea to working backend
• Directus (GPL-3.0, 28K+ stars) wraps any existing SQL database with REST and GraphQL APIs — the BaaS for teams with existing data
• Nhost (MIT, 8K+) provides GraphQL via Hasura auto-generated from your PostgreSQL schema
• Firebase's per-operation pricing becomes expensive above 100K MAU; self-hosted BaaS costs a fixed $8–20/month regardless of user count

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What BaaS Actually Gives You

Backend-as-a-Service tools bundle the backend services that most applications need:

1. Database — Structured data storage with querying
2. Authentication — User registration, login, session management, social login
3. Storage — File upload and CDN delivery
4. Realtime — WebSocket subscriptions for live data
5. Functions — Serverless code execution at the edge

Building these independently takes weeks. BaaS tools give you production-ready implementations in an afternoon. The trade-off is opinionated architecture — you build to the BaaS's data model and API contracts.

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Supabase — Best Firebase Replacement

Supabase has become the default Firebase alternative for good reason: it's PostgreSQL, so your data is in a real relational database with full SQL, indexes, and the entire PostgreSQL extension ecosystem. Firebase's Firestore is a NoSQL document store — migrating data out is painful. Migrating out of Supabase is a standard PostgreSQL export.

Row Level Security (RLS) is Supabase's most powerful feature for building secure applications. You define policies directly on PostgreSQL tables that determine which users can read or write which rows. The policy evaluates on every query, enforced by the database itself:

-- Only users can read their own records
CREATE POLICY "Users can read own records"
ON profiles
FOR SELECT
USING (auth.uid() = user_id);

-- Only admins can delete records
CREATE POLICY "Admins can delete"
ON records
FOR DELETE
USING (
  EXISTS (
    SELECT 1 FROM user_roles
    WHERE user_id = auth.uid()
    AND role = 'admin'
  )
);

This RLS approach means client-side code can query the database directly without a backend API layer — Supabase's JavaScript client handles authentication and the policies enforce data isolation.

# Supabase self-hosted requires multiple services
# Use the official self-hosted setup:
git clone --depth 1 https://github.com/supabase/supabase
cd supabase/docker
cp .env.example .env
# Edit .env with your secrets, then:
docker compose pull
docker compose up -d
# Access dashboard at localhost:3000

Edge Functions run Deno TypeScript at the edge — close to your users for low latency. They have access to your Supabase database and can call external APIs, making them suitable for webhooks, complex auth flows, and server-side operations.

Realtime subscriptions broadcast database changes to connected clients:

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

const supabase = createClient('https://your-project.supabase.co', 'anon-key')

// Subscribe to new messages in a chat room
const subscription = supabase
  .channel('room-1')
  .on(
    'postgres_changes',
    { event: 'INSERT', schema: 'public', table: 'messages', filter: 'room_id=eq.1' },
    (payload) => console.log('New message:', payload.new)
  )
  .subscribe()

Key features:

• PostgreSQL with full SQL support
• Auto-generated REST API (PostgREST) from schema
• GraphQL API (via pg_graphql extension)
• Row Level Security (database-enforced access control)
• Auth with 20+ social providers
• Storage with CDN and image transformations
• Edge Functions (Deno runtime)
• Realtime database subscriptions
• Dashboard (Supabase Studio)
• 20+ official client libraries

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Appwrite — Best Multi-Platform SDK Coverage

Appwrite's differentiator is its SDK breadth. If you're building a product that targets iOS, Android, React, Flutter, and web simultaneously — Appwrite has first-party SDKs for all of them. Firebase competes here, but Appwrite's SDKs are open source and self-hostable.

Appwrite Functions is more flexible than Supabase's Edge Functions. You write serverless functions in Node.js, Python, PHP, Ruby, Swift, Dart, or Go — choose the language your team already knows. Functions run in Docker containers with configurable CPU and memory.

The database is document-based (MariaDB under the hood) with a JSON-like document model similar to Firestore but without Firebase's complex pricing. You define collections and documents through the SDK or dashboard, and Appwrite handles indexing, querying, and permissions.

// Appwrite SDK (same pattern across all platforms)
import { Client, Account, Databases } from "appwrite";

const client = new Client()
  .setEndpoint('https://appwrite.yourdomain.com/v1')
  .setProject('your-project-id');

const account = new Account(client);
const databases = new Databases(client);

// Create a user account
const session = await account.create(
  ID.unique(), 'user@example.com', 'password', 'Full Name'
);

// Query documents with permissions
const posts = await databases.listDocuments(
  'main',           // database ID
  'posts',          // collection ID
  [Query.equal('published', true), Query.orderDesc('created_at')]
);

Appwrite's Teams and Permissions system handles multi-tenant access control. Create teams (organizations, groups, roles), add users to teams, and grant/revoke permissions on documents based on team membership.

Key features:

• Document database (MariaDB-backed)
• SDKs for 10+ platforms (iOS, Android, Flutter, React, Vue, Next.js, Node.js, Python, Go, etc.)
• Auth with 30+ OAuth providers
• Functions in 8+ languages
• Storage with image manipulation
• Realtime events
• Console UI
• Self-hosted with Docker Compose

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PocketBase — Best for Prototyping and Small Apps

PocketBase is remarkable for its simplicity. The entire backend — database, auth, storage, realtime, and admin UI — ships as a single Go binary smaller than 5 MB. No Docker, no Kubernetes, no multiple containers. Download it, run it, have a backend.

For side projects, MVPs, and internal tools, PocketBase dramatically lowers the operational burden. A Raspberry Pi can run a PocketBase backend serving thousands of users.

# PocketBase setup — download and run
wget https://github.com/pocketbase/pocketbase/releases/latest/download/pocketbase_linux_amd64.zip
unzip pocketbase_linux_amd64.zip
./pocketbase serve --http="0.0.0.0:8090"
# Admin UI at localhost:8090/_/

PocketBase stores data in SQLite — embeddable, zero-configuration, and file-based. A backup is as simple as copying the .db file. For production use with concurrent write workloads, SQLite's write locking can be a bottleneck — at that point, migrate to Supabase or Appwrite.

PocketBase can be extended via hooks written in Go. You compile PocketBase as a library and add custom handlers:

package main

import (
    "github.com/pocketbase/pocketbase"
    "github.com/pocketbase/pocketbase/core"
)

func main() {
    app := pocketbase.New()

    app.OnRecordCreate("orders").Add(func(e *core.RecordEvent) error {
        // Custom logic: send a confirmation email, update inventory, etc.
        return e.Next()
    })

    app.Start()
}

Key features:

• Single Go binary (5 MB, zero dependencies)
• SQLite database
• REST API auto-generated from collections
• Auth with social login
• File storage with local or S3 backend
• Realtime subscriptions
• Admin UI
• Hooks for custom logic (Go)
• 128 MB RAM

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Directus — Best for Existing Data

Directus takes a different approach: instead of creating a new database, it wraps your existing SQL database. Point Directus at a PostgreSQL, MySQL, SQLite, or MSSQL database, and it automatically generates REST and GraphQL APIs, an admin interface, and access control — without touching your schema.

This makes Directus the right choice when you already have data. A team with a PostgreSQL database powering their main application can add Directus alongside it to get an admin dashboard and API without migrating to a new system.

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Full Comparison

Feature	Supabase	Appwrite	PocketBase	Directus
License	Apache-2.0	BSD-3	MIT	GPL-3.0
Database	PostgreSQL	MariaDB	SQLite	Any SQL
Stars	73K+	45K+	41K+	28K+
Min RAM	4–8 GB	4 GB	128 MB	512 MB
REST API	✅ PostgREST	✅	✅	✅
GraphQL	✅	✅	❌	✅
Realtime	✅	✅	✅	✅
Functions	✅ Deno	✅ Multi-lang	✅ (hooks)	✅ Flows
SDK Coverage	20+	10+ platforms	JS/Dart	JS/Python
Row-Level Security	✅ PostgreSQL	✅	✅	✅
Self-Host Complexity	High	Medium	Very Low	Medium

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Decision Framework

Choose Supabase if: You want the most complete Firebase replacement with PostgreSQL, advanced RLS, and production-grade performance. Best for applications that will scale.

Choose Appwrite if: You're building multi-platform (web + iOS + Android) and want first-party SDKs for every target. Functions in your preferred language.

Choose PocketBase if: You need a backend in 5 minutes with minimal infrastructure. Side projects, internal tools, MVPs.

Choose Directus if: You have an existing SQL database and want to add an admin interface and API without migrating to a new system.

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Cost Comparison

Scale (100K MAU)	Firebase Blaze	Supabase Self-Hosted	PocketBase
Monthly cost	$200–500+	$20 (VPS)	$5–8 (VPS)
Annual cost	$2,400–6,000	$240	$60–96

Firebase's per-operation pricing is unpredictable and can spike dramatically with a viral event. Self-hosted BaaS has flat, predictable infrastructure cost.

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Related: Supabase vs Appwrite: BaaS Compared · PocketBase vs Supabase: Which Backend? · Best Open Source Firebase Alternatives · How to Self-Host Supabase

See open source alternatives to Firebase on OSSAlt.