Screener

Screener is a private, low-latency screen-sharing project for one game player and a small group of friends. Its accepted media target is WebRTC P2P-first, with an SFU virtual parent feeding only the necessary roots and optional authenticated TURN for explicitly supported restrictive networks. Roots continue distributing to bounded peer descendants; this is not an always-SFU conferencing design. 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. Rooms default to a private fragment invitation whose capability authorizes only one room; a Host may explicitly choose public watching by room code after site access. During a share, the host can change between three ceiling profiles without reopening the source picker: 1080p60 at 8 Mbps, 1080p30 at 5 Mbps, and 720p30 at 3 Mbps. The host can also temporarily pause the picture or switch sources. Rooms are random and temporary by default. A site-access-protected deployment can optionally use SQLite-backed room numbers starting at 1, reusable links, and a waiting state after sharing stops. Default routing gives each viewer an independent direct WebRTC connection; the exact-room controller can instead use bounded peer descendants and LiveKit SFU roots. 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 broadly validated production release. Production runs d4bc421 with room-scoped Viewer access, neutral anonymous entry, initial-connect recovery, and exact-room quality reparenting; it uses self-hosted STUN-only ordinary ICE plus a separate LiveKit SFU/UDP domain. Current source also contains a no-go Native v2 candidate with no production runtime gate. Real cross-network 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

Production requires an independent 8-128 byte visible-ASCII SITE_ACCESS_PASSWORD. It protects room creation, Host role, and code-only Viewer entry. A valid room-scoped fragment grant enters directly without it; otherwise public-watch needs site access plus the room code, and private code-only entry additionally needs the room password. Local development and tests may leave it empty.

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 local default has no STUN, so cross-network use still requires HTTPS and the production ICE configuration documented separately.

Production keeps a stopped v1 SQLite backup and restore boundary as documented in Deployment. SITE_ACCESS_PASSWORD supplies site access; valid private fragment grants bypass that gate, while code-only entry requires site access before public/private room policy is evaluated. The release has no v1 parser, old cookie, or dual-schema runtime. Ordinary ICE contains only self-hosted STUN, LiveKit serves normally one or two SFU/UDP roots, and exhausted paths fail clearly after bounded recovery. Optional generation-bound TURN for a selected exceptional edge is not implemented; HTTPS/WSS remains TLS/TCP independently.

Run the complete automated validation with:

npm run check

Start here:

• Requirements
• WebRTC PoC design
• Deployment and media transport
• Feasibility research
• Current project memory
• Current status
• Architecture decision
• Contributing and Git workflow
• Documentation index