# Cloudflare Realtime SFU Reference

Expert guidance for building real-time audio/video/data applications using Cloudflare Realtime SFU (Selective Forwarding Unit).

## Reading Order

| Task | Files | ~Tokens |
|------|-------|---------|
| New project | README → configuration | ~1200 |
| Implement publish/subscribe | README → api | ~1600 |
| Add PartyTracks | patterns (PartyTracks section) | ~800 |
| Build presence system | patterns (DO section) | ~800 |
| Debug connection issues | gotchas | ~700 |
| Scale to millions | patterns (Cascading section) | ~600 |
| Add simulcast | patterns (Advanced section) | ~500 |
| Configure TURN | configuration (TURN section) | ~400 |

## In This Reference

- **[configuration.md](configuration.md)** - Setup, deployment, environment variables, Wrangler config
- **[api.md](api.md)** - Sessions, tracks, endpoints, request/response patterns
- **[patterns.md](patterns.md)** - Architecture patterns, use cases, integration examples
- **[gotchas.md](gotchas.md)** - Common issues, debugging, performance, security

## Quick Start

Cloudflare Realtime SFU: WebRTC infrastructure on global network (310+ cities). Anycast routing, no regional constraints, pub/sub model.

**Core concepts:**
- **Sessions:** WebRTC PeerConnection to Cloudflare edge
- **Tracks:** Audio/video/data channels you publish or subscribe to
- **No rooms:** Build presence layer yourself via track sharing (see patterns.md)

**Mental model:** Your client establishes one WebRTC session, publishes tracks (audio/video), shares track IDs via your backend, others subscribe to your tracks using track IDs + your session ID.

## Choose Your Approach

| Approach | When to Use | Complexity |
|----------|-------------|------------|
| **PartyTracks** | Production apps with device switching, React | Low - Observable-based, handles reconnections |
| **Raw API** | Custom requirements, non-browser, learning | Medium - Full control, manual WebRTC lifecycle |
| **RealtimeKit** | End-to-end SDK with UI components | Lowest - Managed state, React hooks |

**Recommendation:** Start with PartyTracks for most production applications. See patterns.md for PartyTracks examples.

## SFU vs RealtimeKit

- **Realtime SFU:** WebRTC infrastructure (this reference). Build your own signaling, presence, UI.
- **RealtimeKit:** SDK layer on top of SFU. Includes React hooks, state management, UI components. Part of Cloudflare AI platform.

Use SFU directly when you need custom signaling or non-React framework. Use RealtimeKit for faster development with React.

## Setup

Dashboard: https://dash.cloudflare.com/?to=/:account/calls

Get `CALLS_APP_ID` and `CALLS_APP_SECRET` from dashboard, then see configuration.md for deployment.

## See Also

- [Orange Meets Demo](https://demo.orange.cloudflare.dev/)
- [Orange Source](https://github.com/cloudflare/orange)
- [Calls Examples](https://github.com/cloudflare/calls-examples)
- [API Reference](https://developers.cloudflare.com/api/resources/calls/)
- [RealtimeKit Docs](https://developers.cloudflare.com/workers-ai/realtimekit/)