One npm install — server, client, shared types, CRDTs, and Web Worker all included. Self-hosted, Apache-2.0, free forever.
Written entirely in TypeScript with strict mode end-to-end. Server, client, shared types, Web Worker, and .d.ts declarations — all from a single npm install. No codegen, no separate client/server packages. ESM, CJS, and IIFE bundles included.
React, Vue, Svelte, React Native, vanilla JS on the frontend. Express, NestJS, Fastify, http.createServer() on the backend. ESM, CJS, and IIFE bundles. Drop it into any existing project.
WebSocket runs in a dedicated Web Worker — your UI thread never touches network I/O. Every binary frame >256 B is compressed with pako in user-space. No permessage-deflate negotiation, no per-connection zlib state, no browser compat issues.
9-byte binary frame headers with pako compression. 60–80% smaller than JSON text on the wire. The entire client + worker is ~37.5 KB gzip.
Built for production workloads with thousands of concurrent connections. Not a weekend project — a deeply tested, observable, and scalable framework with end-to-end benchmarks on every CI run.
Server mutates state, clients get diffs — not full snapshots. JSON Patch operations mean the wire carries only what changed. No manual diffing code to write.
LWW registers, PN counters, LWW maps — conflict-free bidirectional sync out of the box. Multiple clients edit the same data structure concurrently with guaranteed convergence.
Multiplexed request/response with correlation IDs, timeouts, and concurrent in-flight. TypeScript generics flow from server handler to client call site — no codegen step.
Server broadcast (stock tickers, notifications) and client-to-server fire-and-forget (analytics, chat). Type-safe, multiplexed on the same connection.
RPC, events, live state, CRDTs, sync channels, sessions — use one or all seven on the same connection. No mode switches, no channel subscriptions, no routing config. They just work together.
In-memory (default), Redis (ioredis), or PostgreSQL (pg). Session persistence across disconnections. Change streams for external event systems.
Rate limit at the WebSocket frame level, not HTTP. Per-method rules. DefaultRateLimiter uses the configured StateBackend — automatically distributed with Redis or Postgres.
Control when diffs reach clients: immediate (latency-sensitive), batched (throughput), or debounced (user input). Per-key configuration.
Prometheus and OpenTelemetry metric exporters. Connection counts, message rates, latency histograms, error rates. Bundle size tracking in CI.
Open source, corp-friendly license. No per-message pricing. No vendor lock-in. No "enterprise tier for production use." Self-host on your infra, your terms.
Swap in Redis or Postgres endpoints and go from single-process to distributed — zero code changes. Three concurrency models (async, thread, thread-pool). pm2/k8s ready. Horizontal scaling is built in, not a pricing tier.
Start with the Developer Guide for integration into existing apps, then use the 10-step tutorial for a full walkthrough from hello-world to production.
Use one, or combine them freely on a single WebSocket connection:
| Pattern | Direction | What it does |
|---|---|---|
| RPC | client → server → client | Typed request/response with correlation IDs |
| Server events | server → clients | Broadcast to all connected clients |
| Client events | client → server | Fire-and-forget (chat, analytics, telemetry) |
| Live state | server → clients | Automatic JSON Patch sync (dashboards, boards) |
| CRDT sync | client ↔ server | Conflict-free merge (collaborative editing) |
| Sync channels | configurable | Immediate, batched, or debounced flush per key |
| Combinations | any | All patterns compose on one connection |
No other library gives you all seven as first-class APIs on one connection. See Composability for examples of combining patterns (dashboard + actions, chat + presence, collab + voting, analytics pipeline).
Measured end-to-end with headless Chromium against a live Node.js server — not synthetic microbenchmarks. Every gate run re-measures. Web Worker transport and pako compression enabled (defaults).
| What | Result | What it means |
|---|---|---|
| RPC round-trip | p50 < 0.5 ms | Call a server function and get a typed response back in under half a millisecond |
| RPC small payload | p50 < 0.4 ms | Tiny JSON body under compression threshold — minimal overhead |
| RPC large JSON | p50 ~18 ms | Randomized ~1 KB JSON payload, pako-compressed on the wire |
| Binary frame streaming | ~6,900 frames/s | Server pushes 1 KB binary-like frames (audio/video metadata) at max rate |
| Two-way game tick | p50 ~4 ms | Client emit → server echo → client ack — full round-trip at emit speed |
| Server event broadcast | ~920 events/s | Push live updates to connected clients at nearly 1,000 events per second |
| Client fire-and-forget | ~235K events/s | Client → server emit throughput: 235,000+ events per second |
| CRDT sync | ~1,300 ops/s | Conflict-free counter increments with full round-trip sync |
| Mixed workload | p50 < 0.4 ms | RPC + events + state combined — sub-millisecond median under mixed load |
| Main-thread blocking | near zero | With Web Worker transport, the UI thread sees no Long Tasks even under flood load |
| Console errors | zero | Zero browser console errors or warnings across all benchmark scenarios |
3 s sustained load per scenario, single Node.js process, Chromium browser. Main-thread impact measured via Long Tasks API + rAF jitter. Console health tracked per-scenario. Full benchmark results, historical trends, and charts →
Client bundles inline everything for zero-dependency browser use. Server and shared bundles externalize runtime deps.
| Bundle | Loaded by | Raw | Gzip |
|---|---|---|---|
| Client IIFE (min) | <script> tag | 72.0 KB | 22.2 KB |
| Worker IIFE (min) | Web Worker | 48.3 KB | 15.3 KB |
| Shared (CJS) | import from bundler | 15.3 KB | 4.0 KB |
| Server (CJS) | Node.js require | 72.1 KB | 16.1 KB |
datasole is a good fit anywhere you need performant, scalable realtime communication:
| Category | Examples |
|---|---|
| Games | Multiplayer lobbies, turn-based games, realtime scoreboards |
| Internal tools | Admin dashboards, monitoring panels, ops consoles |
| Analytics | Live metrics dashboards, A/B test monitors, funnel viewers |
| Native apps | Bun single-executable, Node SEA, Electron, Tauri — with rich web UIs |
| Streaming | Internet radio, watch parties, live commentary sync |
| Local servers | Dev tool frontends, CLI web UIs, process managers |
| Collaboration | Shared whiteboards, collaborative editing, design tools |
| IoT | Device control panels, telemetry viewers, sensor networks |
| Finance | Trading data feeds, portfolio trackers, auction platforms |
| Communication | Live chat, customer support, classroom Q&A |
| DevOps | CI/CD pipeline walls, deployment status, log streaming |
See the full comparison with Socket.IO, Ably, Pusher, Liveblocks, and PartyKit.