Electric SQL Has Free Local-First Sync — Here's How to Build Offline-Ready Apps

What if your app worked offline and synced when connected? Electric SQL makes local-first development practical.

What is Electric SQL?

Electric SQL syncs data between PostgreSQL in the cloud and SQLite on the client. Your app reads and writes locally (instant), and Electric handles the sync.

Why Local-First?

• Instant responses — reads and writes hit local SQLite, not a network round-trip
• Works offline — app functions without internet
• Multi-device sync — changes propagate to all devices
• Conflict resolution — automatic, based on CRDTs

Quick Start

bun add @electric-sql/client

Syncing Data

import { ShapeStream, Shape } from '@electric-sql/client';

// Define a shape (what data to sync)
const stream = new ShapeStream({
  url: 'http://localhost:3000/v1/shape',
  params: {
    table: 'tasks',
    where: 'user_id = 123',
  },
});

const shape = new Shape(stream);

// Subscribe to changes
shape.subscribe((data) => {
  console.log('Tasks updated:', data);
  // data is always the latest synced state
});

// Get current value
const currentTasks = shape.value;

With React

import { useShape } from '@electric-sql/react';

function TaskList({ userId }) {
  const { data: tasks, isLoading } = useShape({
    url: 'http://localhost:3000/v1/shape',
    params: {
      table: 'tasks',
      where: `user_id = '${userId}'`,
    },
  });

  if (isLoading) return <p>Loading...</p>;

  return (
    <ul>
      {tasks.map(task => (
        <li key={task.id}>
          {task.completed ? 'Done' : 'Todo'}: {task.text}
        </li>
      ))}
    </ul>
  );
}

How Sync Works

Client (SQLite)  <---->  Electric  <---->  PostgreSQL

1. Client writes to local SQLite (instant)
2. Electric detects the change
3. Electric syncs to PostgreSQL
4. PostgreSQL change is pushed to all other clients
5. Conflicts resolved automatically via CRDTs

Use Cases

• Note-taking apps — write notes offline, sync later
• Project management — update tasks on the go
• Field data collection — collect data without internet
• Collaborative editing — multiple users, no conflicts
• Mobile apps — seamless online/offline experience

Electric SQL vs Alternatives

Feature	Electric SQL	Firebase	Convex	CRDTs (Yjs)
Local-first	Yes	No	No	Yes
Offline	Full	Partial	No	Yes
Database	PostgreSQL + SQLite	Firestore	Custom	Custom
Conflict Resolution	CRDT	Last-write-wins	ACID	CRDT
Sync	Automatic	Automatic	Automatic	Manual
Schema	PostgreSQL DDL	Schemaless	TypeScript	Custom

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