In this guide, you will master the implementation of PGLite and ElectricSQL to build high-performance, local-first web applications. You will learn how to move beyond traditional REST/GraphQL APIs by deploying a full WASM-powered Postgres instance directly in the browser for zero-latency state management and seamless offline synchronization.
- Architecting apps using the Local-First (LoFi) paradigm to eliminate loading spinners.
- Setting up PGLite as a persistent, reactive browser database with full SQL support.
- Implementing real-time data synchronization between the browser and server using ElectricSQL.
- Managing complex state with reactive local-first schemas and Conflict-free Replicated Data Types (CRDTs).
Introduction
Your users don't care about your sophisticated backend architecture; they care that your app stops working the second they step into an elevator. For years, we have conditioned users to accept "loading spinners" as a fundamental law of the internet. We treated the network as a reliable bridge, only to be burned by latency, jitter, and the inevitable "Offline" modal that kills user engagement.
By April 2026, the industry has reached a breaking point with the traditional Request-Response cycle. This pglite postgres browser tutorial explores the massive shift toward local-first web architecture 2026, where the primary data source isn't a remote server, but a database living inside the user's browser. We are moving away from traditional API overhead in favor of direct browser-to-database synchronization, where the cloud acts as a backup and relay rather than a gatekeeper.
In this guide, we are going to build a collaborative, offline-capable engineering dashboard. We will use PGLite—the WASM-powered Postgres distribution—and ElectricSQL to handle the heavy lifting of synchronization. By the end, you will understand how to implement offline-first state management that feels instantaneous and handles multi-user conflicts without breaking a sweat.
The Death of the API: Why Local-First is Matured
In the old world, every user interaction triggered a fetch request. You clicked a button, waited for the round-trip to the server, waited for the database query, and finally updated the UI. Even with optimistic updates, the complexity of keeping the local UI state in sync with the server was a nightmare of "useEffect" hooks and manual cache invalidation.
Local-first architecture flips the script. You write to a local database first. The UI updates instantly because the data is already there in the browser's memory. A background process—the sync engine—handles the messy work of pushing that change to the server and pulling updates from other users. This is wasm database sync at its finest: the network is an optimization, not a dependency.
Think of it like Git. You commit locally, work offline, and "push" when you have a connection. PGLite brings the full power of Postgres—including joins, constraints, and transactions—to this workflow, allowing you to use reactive local-first schemas that were previously impossible with limited storage like IndexedDB.
PGLite isn't just a "Postgres-like" library; it is the actual Postgres source code compiled to WebAssembly. This means you get full SQL compatibility, including advanced features like JSONB and window functions, directly in the browser.
How PGLite and ElectricSQL Work Together
PGLite provides the storage and the query engine. It lives in a Web Worker, ensuring that heavy SQL queries never block the main UI thread. However, a local database is just an island without a way to talk to the rest of the world. That is where electricsql sync engine react comes into play.
ElectricSQL acts as a bidirectional sync bridge. It watches the Postgres logical replication stream on your server and pushes changes down to the PGLite instance in the browser. When the user makes a change locally, ElectricSQL captures that change and replicates it back up to the master database. It handles the implementing crdts collaboration logic automatically, ensuring that if two users edit the same row while offline, their changes merge predictably rather than just overwriting each other.
This combination solves the hardest problem in distributed systems: partial failure. If the sync engine disconnects, PGLite keeps working. When the connection returns, the sync engine "catches up" by replaying the missing transactions. This is the gold standard for browser postgres performance in 2026.
Key Features and Concepts
WASM-Powered Persistence
PGLite uses the browser's File System Access API or IndexedDB to persist the database files. Unlike older solutions that cleared data on refresh, PGLite ensures your INSERT statements survive a browser restart or a computer reboot.
Reactive Queries
Instead of manual refetching, we use "live queries." You define a SQL query, and the UI automatically re-renders whenever the underlying data changes. This eliminates the need for complex state management libraries like Redux or Zustand for your core data.
Use Postgres Views to simplify your reactive queries. By moving logic into the database layer, your React components stay "dumb" and focused only on rendering the data they receive.
The "Shape" Protocol
ElectricSQL introduces the concept of "Shapes." A shape is a subset of your server-side database that a specific user is allowed to see. You don't sync the whole 10TB production database; you sync the "Shape" of the data relevant to the current user's projects.
Implementation Guide
We are going to build a collaborative task engine. We'll start by initializing PGLite and then hook it into ElectricSQL for real-time synchronization. We assume you have a basic React 19+ environment ready.
// 1. Initialize PGLite with persistence
import { PGLite } from "@electric-sql/pglite";
import { useEffect, useState } from "react";
export const useDatabase = () => {
const [db, setDb] = useState(null);
useEffect(() => {
const initDb = async () => {
// Create or open a persistent Postgres instance
const pg = new PGLite("idb://engineering-db");
// Basic schema setup
await pg.exec(`
CREATE TABLE IF NOT EXISTS tasks (
id UUID PRIMARY KEY,
title TEXT NOT NULL,
status TEXT DEFAULT 'todo',
created_at TIMESTAMP DEFAULT NOW()
);
`);
setDb(pg);
};
initDb();
}, []);
return db;
};In this block, we initialize PGLite using the idb:// prefix, which tells the engine to use IndexedDB for permanent storage. We then run a standard SQL CREATE TABLE command. Notice that this is identical to the SQL you would write for a server-side Postgres instance.
Don't run schema migrations on every page load in production. Use a versioning system or a dedicated migration script to ensure you don't accidentally wipe user data when updating your table structures.
Now, let's look at how we perform a reactive query. This is where the local-first magic happens. We want our UI to update the moment a new task arrives via sync or a local edit.
// 2. Implement a Reactive Live Query
import { useLiveQuery } from "@electric-sql/pglite-react";
const TaskList = ({ db }: { db: PGLite }) => {
// This hook automatically re-runs when the 'tasks' table changes
const tasks = useLiveQuery(
db,
"SELECT * FROM tasks ORDER BY created_at DESC"
);
if (!tasks) return Loading local DB...;
return (
{tasks.rows.map((task) => (
{task.title} - {task.status}
))}
);
};The useLiveQuery hook is the centerpiece of electricsql sync engine react integration. It subscribes to the PGLite transaction log. When any transaction touches the tasks table, the hook triggers a re-render. There is no manual cache invalidation required—the database is the single source of truth.
Finally, we need to connect this local instance to our cloud Postgres via ElectricSQL. This requires a sync service running on your infrastructure (or a managed provider).
// 3. Connecting to the Sync Engine
import { electrify } from "@electric-sql/pglite/sync";
const syncDatabase = async (pg: PGLite) => {
const electric = await electrify(pg, {
url: "https://api.your-production-db.com",
token: "user-auth-token-123"
});
// Define the "Shape" of data to sync
const shape = await electric.db.tasks.sync({
where: { project_id: 'engineering-2026' }
});
// Wait for initial sync to complete
await shape.synced;
console.log("Database is now live-synced!");
};The electrify function wraps our PGLite instance. It establishes a WebSocket connection to the ElectricSQL sync service. By defining a shape, we tell the engine exactly which rows to pull down. This keeps the local database lean and ensures that users only download the data they are authorized to access.
Always use UUIDs for primary keys in local-first apps. Since multiple users are generating IDs offline, standard integer increments will cause collisions the moment they try to sync.
Best Practices and Common Pitfalls
Optimistic UI and Conflict Resolution
In a local-first world, "conflicts" are a feature, not a bug. Because you are implementing crdts collaboration, you don't need to lock rows. However, you should still design your schema to be additive. Instead of a single "status" column that gets overwritten, consider an "events" table that tracks status changes. This allows the sync engine to merge changes more intelligently using causal ordering.
Handling Large Datasets
While browser postgres performance is impressive, mobile devices still have memory constraints. Do not attempt to sync your entire production database to a phone. Use the ElectricSQL Shape protocol to partition data by user, organization, or time. A good rule of thumb is to keep the local PGLite instance under 500MB for optimal performance on mid-range devices.
The "Safari Problem"
Even in 2026, browser vendors have different policies on storage persistence. Safari may clear IndexedDB data if the user hasn't visited the site in several weeks. Always design your app so that the local database can be re-hydrated from the server if it is missing. Local-first means "Local is the primary source," not "Local is the only source."
Real-World Example: Collaborative CAD Software
Imagine a team of engineers designing a new satellite. They are working in a browser-based CAD tool. Traditionally, every move of a component would send a JSON payload to a server, which would then broadcast it to other users. With high latency, the components would "jump" around the screen.
By using PGLite, the CAD tool stores every component coordinate in a local elements table. When an engineer moves a part, the tool runs a SQL UPDATE. The local UI updates at 120fps because it is reading from local WASM memory. In the background, ElectricSQL syncs the coordinate change to the rest of the team. If two engineers move the same part, the CRDT logic resolves the final position based on the latest timestamp or a predefined business rule. The result is a desktop-class experience inside a browser tab.
Future Outlook and What's Coming Next
The next 18 months will see PGLite move toward Peer-to-Peer (P2P) synchronization. We are already seeing RFCs for WebRTC-based sync protocols that would allow two browsers to sync their Postgres instances directly without ever touching a central server. This would further reduce latency and server costs for high-bandwidth collaborative apps.
Additionally, expect to see "Vector Search" integrated directly into PGLite. With the rise of local AI models (WebLLM), having a vector-enabled Postgres instance in the browser will allow developers to build private, local-first RAG (Retrieval-Augmented Generation) applications that process sensitive data without it ever leaving the user's machine.
Conclusion
The transition to local-first architecture isn't just a trend; it is the natural evolution of the web. By moving the database to the edge—literally into the user's browser—we eliminate the largest bottleneck in modern software: the network. PGLite and ElectricSQL provide the tools to do this today without sacrificing the relational power of Postgres.
Stop building apps that break in the elevator. Start building applications that are resilient, instantaneous, and truly user-centric. Your first step is to replace your global "isLoading" state with a persistent PGLite instance. Once you experience the simplicity of a zero-latency UI, there is no going back.
- PGLite brings full Postgres capabilities to the browser via WASM, enabling browser postgres performance that rivals native apps.
- ElectricSQL simplifies wasm database sync by handling the complex logic of bidirectional replication and conflict resolution.
- Reactive queries via
useLiveQueryeliminate the need for manual state management and cache invalidation. - Download the PGLite package today and migrate one small slice of your app state to a local-first model to see the performance gains firsthand.
