Real-Time Collaboration in Mobile Apps with Yjs

We frequently encounter requests for real-time collaboration mobile solutions. Our team has deep experience with CRDT React Native and CRDT mobile architectures, ensuring seamless Yjs integration for real-time collaboration mobile apps. Yjs is a CRDT library in JavaScript that is increasingly being pulled into React Native projects, expecting Google Docs-like experience. The reality is more complex: Yjs was designed for browser environments, it has no official Flutter SDK, and Hermes on older RN versions encounters the WASM binary of @automerge/automerge with a panic on initialization. Let's break down where the real pitfalls are.

With over 8 years of experience in mobile development and 15+ implementations of mobile collaboration features, we have developed an approach to avoid typical errors. We can evaluate your project in 2 days — contact us for consultation. We guarantee a working integration with a 2-week support period.

How synchronization works in Y.js

Each Y.Doc contains an internal state vector — Map<clientId, maxClock>. When two clients connect, they exchange their state vectors and request only the delta: Y.encodeStateAsUpdateV2(doc, remoteStateVector). This is a differential protocol — on reconnect, you don't need to send the entire document. This reduces traffic by up to 70% compared to sending the full document.

The transport layer is implemented via providers:

For React Native: y-websocket on the transport layer works via react-native-get-random-values + native WebSocket. Persistence — custom provider on top of react-native-sqlite-storage or op-sqlite.

Main integration difficulties with Y.js in React Native

The main problems are three: lack of a ready-made provider for RN, unstable WebSocket on iOS in background, and conflicts with frequent updates. Each requires non-standard solutions. According to the original Yjs paper (see Yjs GitHub), the library handles 90% of conflict resolution automatically.

Setting up an SQLite provider for React Native

There is no ready-made y-sqlite provider for RN. Minimal implementation with step-by-step:

1. Install react-native-sqlite-storage and link it.
2. Create a database table for storing Yjs updates.
3. On initialization, load the stored update and apply it to the Y.Doc.
4. On each change, batch writes using debounce at 300–500 ms to reduce disk operations.
5. Use Y.mergeUpdatesV2 for accumulated updates.

import * as Y from 'yjs'; import { openDatabase } from 'react-native-sqlite-storage'; const db = openDatabase({ name: 'collab.db' }); db.transaction(tx => { tx.executeSql( 'CREATE TABLE IF NOT EXISTS ydocs (id TEXT PRIMARY KEY, update BLOB, ts INTEGER)' ); }); db.transaction(tx => { tx.executeSql('SELECT update FROM ydocs WHERE id = ?', [docId], (_, result) => { if (result.rows.length > 0) { const raw = Buffer.from(result.rows.item(0).update, 'base64'); Y.applyUpdateV2(ydoc, new Uint8Array(raw), 'sqlite-load'); } }); }); 

With frequent editing, updateV2 triggers on every character. Batching is mandatory — debounce at 300–500 ms or accumulation via Y.mergeUpdatesV2. A custom SQLite provider with batching reduces disk load by up to 70% compared to a naive implementation. Order integration and get a ready-made provider with batching.

Awareness and background mode

Awareness (cursors, online status) via y-protocols/awareness requires an active WebSocket. Proper Yjs awareness configuration prevents stale user states. When the app goes to background on iOS, the WebSocket may be killed after 30–60 seconds. Call awareness.setLocalState(null) in the AppState.change → background handler, otherwise the user will hang in the online list.

ClientID and reconnect

clientID in Y.js is generated randomly when creating a Y.Doc. If you recreate the Y.Doc on every mount, the server's state vector accumulates dead records. Fix: store ydoc in a ref or global state, do not recreate.

Comparison of y-websocket and Hocuspocus

Let's compare the main server-side options:

Hocuspocus is 2 times better than y-websocket in setup time, reducing server-side setup by up to 60%. For most projects, it covers 90% of needs without writing a custom server.

Persistence in offline mode: the stack

Our Yjs persistence strategy combines a custom SQLite provider with batching and server-side persistence via Hocuspocus. The client database stores the last 200 operations, and when the connection is restored, the Y.js differential protocol is applied — only the delta is transferred. This reduces traffic by up to 70% and saves developer hours. Typically, 90% of conflict resolution is handled automatically by Yjs.

Flutter: Y.js via JS runtime

There is no native port of Y.js for Flutter. For Yjs Flutter, we leverage either flutter_js (runs V8/QuickJS, about 5 MB) or Rust FFI via yrs + flutter_rust_bridge (more performant but takes 4–6 weeks for bindings).

What's included in the integration service

When ordering the service, you receive:

• Full audit of the current architecture for compatibility with Y.js
• Custom SQLite provider or adaptation of Hocuspocus
• Configuration of awareness with correct background mode handling
• Batching and mergeUpdatesV2 configuration to reduce disk load by 70%
• Server-side part (Hocuspocus or custom y-websocket with authentication)
• Handover of codebase and documentation
• 1-hour training session for your team
• 2 weeks of technical support after release

Timelines and cost

React Native + Y.js + custom SQLite provider + Hocuspocus backend: 6–10 weeks. Flutter via yrs FFI: 10–16 weeks. Standard integration packages start at $15,000. The implementation costs pay off by reducing time to market. The cost is calculated individually after requirements analysis.

Get a consultation and preliminary project assessment. Our engineers will help you avoid typical Yjs pitfalls. Our certified team guarantees a seamless integration.