# PouchDB — JavaScript Database That Syncs Everywhere

> PouchDB is an open-source JavaScript database inspired by CouchDB that runs in the browser, Node.js, or Electron. It enables offline-first applications by syncing data seamlessly with CouchDB-compatible servers when connectivity is available.

## Install

Save in your project root:

# PouchDB — JavaScript Database That Syncs Everywhere

## Quick Use
```bash
npm install pouchdb
```
```js
const PouchDB = require('pouchdb');
const db = new PouchDB('mydb');
await db.put({ _id: 'doc1', title: 'Hello' });
const doc = await db.get('doc1');
```

## Introduction
PouchDB brings the power of CouchDB's replication protocol to JavaScript, letting you store data locally in the browser or Node.js and sync it to a remote server when online. It is the go-to solution for building offline-first web and mobile applications.

## What PouchDB Does
- Stores JSON documents in IndexedDB, WebSQL, or LevelDB depending on environment
- Implements the CouchDB replication protocol for bidirectional sync
- Works in browsers, Node.js, Cordova, Electron, and React Native
- Provides a Promise-based API compatible with the CouchDB query model
- Supports plugins for full-text search, authentication, and more

## Architecture Overview
PouchDB is an adapter-based system where a storage adapter (IndexedDB in browsers, LevelDB in Node) handles persistence while the replication engine manages sync with any CouchDB-protocol server. Conflict resolution follows CouchDB's revision-tree model, picking a deterministic winner while preserving conflicting revisions for manual resolution.

## Self-Hosting & Configuration
- Install via npm for Node or include the browser bundle via CDN
- Pair with CouchDB, IBM Cloudant, or PouchDB Server as the remote
- Configure replication with `db.sync(remoteURL, { live: true, retry: true })`
- Use the pouchdb-find plugin for Mango-style queries
- Set up filtered replication to sync only relevant documents per user

## Key Features
- Offline-first by design with automatic conflict detection
- Cross-platform: same API in browser, server, and mobile
- Live replication keeps local and remote databases in sync in real time
- Rich plugin ecosystem for indexing, encryption, and authentication
- Lightweight at about 46 KB minified and gzipped for the browser build

## Comparison with Similar Tools
- **CouchDB** — PouchDB is the client-side counterpart; CouchDB is the server
- **RxDB** — built on top of PouchDB/RxStorage with reactive queries; more opinionated
- **Dexie.js** — IndexedDB wrapper without built-in sync; PouchDB adds replication
- **WatermelonDB** — optimized for React Native with lazy loading; PouchDB is more universal
- **Firebase Firestore** — proprietary cloud sync; PouchDB is open source and self-hostable

## FAQ
**Q: Can PouchDB sync with databases other than CouchDB?**
A: It syncs with any server implementing the CouchDB replication protocol, including IBM Cloudant and PouchDB Server.

**Q: How does PouchDB handle conflicts?**
A: It uses CouchDB's revision tree model, deterministically picking a winner while storing conflicting revisions so you can resolve them in application code.

**Q: Is PouchDB suitable for large datasets?**
A: It works well for thousands to tens of thousands of documents. For very large datasets, consider server-side querying with selective replication.

**Q: Does PouchDB support encryption?**
A: The core does not, but the comdb or crypto-pouch plugins add transparent encryption at rest.

## Sources
- https://github.com/pouchdb/pouchdb
- https://pouchdb.com/guides/

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Source: https://tokrepo.com/en/workflows/b5464b81-3b63-11f1-9bc6-00163e2b0d79
Author: AI Open Source