Screener is a private, low-latency screen-sharing project for one game player and a small group of friends. Its media path is WebRTC P2P-first, with authenticated TURN fallback for network pairs that cannot connect directly. Viewers should be able to join from a desktop or mobile browser without installing the sender application.

The first measurable Web proof of concept is implemented. A host captures a screen, window, or browser tab and shares a numeric room code; friends can open /r/{code} directly or enter the code at /join, with no separate viewer token. Rooms are random and temporary by default. A password-protected deployment can optionally use SQLite-backed room numbers starting at 1, reusable links, and a waiting state after sharing stops. Each viewer currently receives an independent WebRTC connection, so direct and TURN-relayed paths can coexist in one room. The default room capacity is eight viewers and deployments may configure 1 through 16, but that admission limit is not a performance promise.

This is not yet a production release. Public TURN/UDP and TURN/TCP relay paths are verified, but real cross-network Screener media, game audio, a sustained 1:8 room, mobile browser lifecycle behavior, and latency targets still require the documented manual test matrix.

Run locally

Node.js 24 and npm 11 are required.

npm ci
npm run dev

ACCESS_PASSWORD is optional. Leaving it empty makes the site public; setting it gates both hosting and viewing behind one site-wide password. Internet deployments intended to stay private should set it, because in public mode the numeric room code is the only viewing capability and does not provide strong privacy by itself.

Open http://localhost:8787. The server listens on 0.0.0.0 by default so a phone on the same LAN can load http://<computer-lan-ip>:8787. To generate an invite that the phone can open while the host keeps using secure-context localhost capture, set PUBLIC_BASE_URL to that LAN URL and include both origins in ALLOWED_ORIGINS. LAN viewers can join over HTTP; the sharing page must remain on localhost or HTTPS because screen capture requires a secure context. The default has no STUN or TURN, so cross-network use still requires HTTPS and the production ICE configuration documented separately.

Production startup requires STUN plus separate TURN/UDP and TURN/TCP URLs. TURN/TLS is an optional restrictive-network enhancement: use its standard TCP port 5349 by default, or port 443 only when the deployment has a dedicated public IP or a validated layer-4/SNI route. This configuration preflight is not evidence that any external relay path works.

Run the complete automated validation with:

npm run check

Start here: