Loro

Make your JSON data collaborative and version-controlled 🦜

Documentation

|

Getting Started

|

Rust Doc

✨ Loro 1.0 is out! Read the announcement.

Loro is a CRDTs(Conflict-free Replicated Data Types) library that makes building [local-first][local-first] and collaborative apps easier. You can now use it in Rust, JS (via WASM), and Swift.

Features

Features Provided by CRDTs

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

Supported CRDT Algorithms

- 📝 Text Editing with [Fugue]
- 📙 Rich Text CRDT
- 🌲 Moveable Tree
- 🚗 Moveable List
- 🗺️ Last-Write-Wins Map

Advanced Features in Loro

- 🚀 Fast Document Loading
- ⏱️ Fast Time Travel Through History
- 🏛️ Version Control with Real-Time Collaboration
- 📦 Shallow Snapshot that Works like Git Shallow Clone

> In this example, we demonstrate importing an entire Loro codebase into a Loro-powered
> version controller, preserving the complete Git DAG history while enabling fast version switching.

Debugging the Wasm build

The standard build pipeline (deno run -A ./scripts/build.ts dev|release) now keeps DWARF debugging information through wasm-bindgen and emits two helper files alongside every loro_wasm_bg.wasm artifact:

- loro_wasm_bg.wasm.map — a v3 source map derived from DWARF so that Chrome, Edge, and Firefox can show original Rust locations when inspecting stack traces.

Load the source map in browser devtools; when devtools fetches the debug companion it can map instructions back to Rust source files and line numbers without inflating the shipped .wasm.

Example


``ts
import { expect, test } from 'vitest';
import { LoroDoc, LoroList } from 'loro-crdt';

test('sync example', () => {
// Sync two docs with two rounds of exchanges

// Initialize document A
const docA = new LoroDoc();
const listA: LoroList = docA.getList('list');
listA.insert(0, 'A');
listA.insert(1, 'B');
listA.insert(2, 'C');

// Export all updates from docA
const bytes: Uint8Array = docA.export({ mode: 'update' });

// Simulate sending bytes across the network to another peer, B

const docB = new LoroDoc();
// Peer B imports the updates from A
docB.import(bytes);

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

// Get the current version of docB
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 sync point
const bytesB: Uint8Array = docB.export({ mode: 'update', from: version });

// Simulate sending bytesB back across the network to A

// A imports the updates from B
docA.import(bytesB);

// A has the same state as B
expect(docA.toJSON()).toStrictEqual({
list: ['A', 'C'],
});
});
``

Blog

- Loro 1.0
- Movable tree CRDTs and Loro's implementation
- Introduction to Loro's Rich Text CRDT
- Loro: Reimagine State Management with CRDTs

Credits

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

- Diamond-types: The Event Graph Walker (Eg-walker) 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 work.
- 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.

[local-first]: https://www.inkandswitch.com/local-first/
[Fugue]: https://arxiv.org/abs/2305.00583