Blendr

Watch YouTube together. Perfect sync. Zero screenshare.

Blendr lets one host control playback from YouTube while everyone else joins from a clean browser link.

Website · Chrome Extension · Demo · Runbook · Protocol

What It Does

Blendr turns a normal YouTube tab into a watch party host. The admin starts a session from the Chrome extension, shares the generated Blendr link, and viewers stay locked to the host's playback state without a screenshare, meeting room, or shared account.

The current production stack is live at:

Surface	URL
Website	https://blendr.live
API	https://api.blendr.live
Chrome extension	Chrome Web Store ID dhijdnhjdpoiegbagdcjgaokoljgdbno

How It Works

1. The admin opens a YouTube video and starts broadcasting from the Chrome extension.
2. The extension creates a session with POST /api/session/create, then connects as the authenticated admin over WebSocket.
3. The content script reads the YouTube <video> state and sends sync packets through the background service worker.
4. The API keeps session state in memory, tracks session metadata in Redis, and broadcasts state to viewers.
5. Viewers open https://blendr.live/watch?session=...; the website connects as a read-only viewer and drives the YouTube IFrame player.

Repository Layout

blendr/
├── apps/
│   ├── website/          # Next.js viewer app deployed by Vercel
│   ├── api/              # Bun WebSocket/API server deployed on GCP
│   └── admin-extension/  # Chrome MV3 admin broadcaster extension
├── docs/
│   ├── PROTOCOL.md       # HTTP/WebSocket protocol and session lifecycle
│   └── RUNBOOK.md        # Local dev, deploy, release, and operations
├── infra/
│   ├── caddy/            # Production reverse proxy config
│   └── systemd/          # Production API service unit
├── scripts/
│   ├── dev-local.sh
│   ├── start-api.sh
│   ├── deploy-api.sh
│   └── package-extension.sh
├── AGENTS.md
├── LICENSE
├── package.json
├── pnpm-workspace.yaml
└── vercel.json

Local Development

Prerequisites:

• Bun 1.1+
• Node.js 18+
• npm or pnpm
• Chrome for extension testing

Start the full local stack:

./scripts/dev-local.sh

Access points:

Service	URL
Website	http://localhost:3000
API	http://localhost:6767/api/session/create
WebSocket	ws://localhost:6767/ws

Manual commands:

cd apps/api && bun run dev
cd apps/website && npm run dev

For extension testing, load apps/admin-extension as an unpacked extension in Chrome. scripts/dev-local.sh temporarily points apps/admin-extension/config.js at localhost and restores production config on exit.

Production

• Website: Vercel builds apps/website using vercel.json.
• API: GCP VM hdtrs, Caddy on ports 80/443, Bun bound to 127.0.0.1:6767, Redis local on 127.0.0.1:6379.
• Extension: packaged from apps/admin-extension; production endpoints must stay https://api.blendr.live and wss://api.blendr.live.

Operational details live in:

• docs/RUNBOOK.md
• docs/PROTOCOL.md

Checks

cd apps/api && bunx tsc --noEmit
cd apps/website && npm run build
./scripts/package-extension.sh

package-extension.sh queries the Chrome update endpoint and refuses to create blendr-admin-extension.zip unless apps/admin-extension/manifest.json is higher than the currently published version.

License

Apache License 2.0. Copyright 2026 Mihir Belose.