01
Concurrent edits converge
Two people type into the same paragraph on different continents. Coalesce interleaves their operations and both screens settle on one text — no lock, no prompt, no “theirs or mine”.
v1.0 · local-first sync engine · MIT
Edits drift apart.
State flows back together.
Coalesce is an open-source CRDT engine for apps that work offline, on every device, at once. Each replica keeps writing on its own. When they meet, they merge — automatically, deterministically, without a server deciding who wins.
Read the quickstart
pnpm add @coalesce/coreHow it merges
Three behaviours, one data structure.
02
Sync you can see
Peers trade changes in the background over any transport you hand it: WebSocket, WebRTC, a USB stick. The status hook tells your UI exactly how many ops are still in flight.
03
Offline is just a branch
A replica that loses signal keeps working on its own copy. When it reconnects, its history buds back into the main document instead of overwriting it.
Quickstart
A few lines from a JSON object to a shared one.
Wrap any plain object in a document, point it at a relay or a peer, and mutate it like you always have. Every change becomes an operation; every operation is safe to apply twice, out of order, a week late.
- 4.1 kB
- core, min + gzip
- MIT
- licence, forever
- 212
- contributors
- 0
- servers required
// board.ts
import { doc } from '@coalesce/core'
const board = doc('kanban', {
peers: 'wss://relay.example.dev',
persist: 'indexeddb',
})
board.change((d) => {
d.columns.todo.push({ title: 'Ship 1.0' })
})
board.status() // → { peers: 6, pending: 0 }Bring your own app.
We'll keep it in one piece.
Coalesce is a fictional project, made to demo a gooey blob system. Built by its community, governed in the open.