Synchronized Playback for External Streaming Sites
Watch together, perfectly in sync — across different browsers and devices. No screen sharing, no video streamed through a server. Only play / pause / seek / speed state is synchronized.
Coming soon — the hosted app and extension links will go live once deployed.
Privacy by design
The video never touches our backend. Each participant loads the same media in their own browser; only tiny play / pause / seek / speed JSON messages are synced.
Millisecond-accurate sync
An NTP-style server-clock estimator plus drift correction keeps viewers within ~1 ms of the host — gentle rate nudges under 1 s of drift, hard-seek beyond it.
Web app + browser extension
Watch in the web app with a shared direct URL, or use the MV3 extension to drive the real <video> on supported external streaming pages — same sync engine either way.
Host authority
The server validates that sync events come from the room's host, re-stamps them into server time, and broadcasts one canonical state to everyone else.
How it works
Create or join a room
The host opens a room and shares the code. Viewers join and load the same media source in their own browser.
Host drives playback
Play, pause, seek, and speed changes from the host are captured with a server-time estimate and sent to the sync server.
Everyone stays in sync
The server broadcasts the authoritative state; each viewer computes the expected position and corrects drift once per tick.
Under the hood
A TypeScript monorepo: a shared sync engine (server-clock offset, expected-position math, drift correction), a WebSocket sync server with in-memory host-authoritative rooms, a Vite + React web app, and an MV3 browser extension — the web app and the extension are separate clients of the same server speaking one protocol.