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

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

Example

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"],
  });
});

DevTools

Loro Inspector

You can use the Loro Inspector to inspect the state and history of a Loro document.