Reimagine state management with CRDTs 🦜
Make your app state synchronized and collaborative effortlessly.

Documentation | Getting Started | Rust Doc

⚠️ Notice: The current API and encoding schema of Loro are experimental and subject to change. You should not use it in production.

Loro is a CRDTs(Conflict-free Replicated Data Types) library that makes building local-first apps easier. It is currently available for JavaScript (via WASM) and Rust developers.

Explore our vision in our blog: ✨ Reimagine State Management with CRDTs.

Basic Features Provided by CRDTs

• P2P Synchronization
• Automatic Merging
• Local Availability
• Scalability
• Delta Updates

Supported CRDT Algorithms

• 📝 Text Editing with Fugue
• 📙 Peritext-like Rich Text CRDT
• 🌲 Moveable Tree
• 🚗 Moveable List
• 🗺️ Last-Write-Wins Map
• 🔄 Replayable Event Graph

Advanced Features in Loro

• 📖 Preserve Editing History in a Replayable Event Graph
• ⏱️ Fast Time Travel Through History

import { expect, test } from 'vitest';
import { Loro, LoroList } from 'loro-crdt';

/**
 * Demonstrates synchronization of two documents with two rounds of exchanges.
 */
// Initialize document A
const docA = new Loro();
const listA: LoroList = docA.getList('list');
listA.insert(0, 'A');
listA.insert(1, 'B');
listA.insert(2, 'C');

// Export the state of document A as a byte array
const bytes: Uint8Array = docA.exportFrom();

// Simulate sending `bytes` across the network to another peer, B
const docB = new Loro();
// Peer B imports the updates from A
docB.import(bytes);

// Verify that B's state matches A's state
expect(docB.toJSON()).toStrictEqual({
  list: ['A', 'B', 'C'],
});

// Get the current operation log version of document B
const version = docB.oplogVersion();

// Simulate editing at B: delete item 'B'
const listB: LoroList = docB.getList('list');
listB.delete(1, 1);

// Export the updates from B since the last synchronization point
const bytesB: Uint8Array = docB.exportFrom(version);

// Simulate sending `bytesB` back across the network to A
// A imports the updates from B
docA.import(bytesB);

// Verify that the list at A now matches the list at B after merging
expect(docA.toJSON()).toStrictEqual({
  list: ['A', 'C'],
});

Loro draws inspiration from the innovative work of the following projects and individuals:

• Ink & Switch: The principles of Local-first Software have greatly influenced this project. The Peritext project has also shaped our approach to rich text CRDTs.
• Diamond-types: The Replayable Event Graph (REG) algorithm from @josephg has been adapted to reduce the computation and space usage of CRDTs.
• Automerge: Their use of columnar encoding for CRDTs has informed our strategies for efficient data encoding.
• Yjs: We have incorporated a similar algorithm for effectively merging collaborative editing operations, thanks to their pioneering works.
• Matthew Weidner: His work on the Fugue algorithm has been invaluable, enhancing our text editing capabilities.
• Martin Kleppmann: His work on CRDTs has significantly influenced our comprehension of the field.