📡 Mac Screencast

Broadcast your Mac screen — with system audio — to any browser on your Wi-Fi: laptops, phones, or a Fire TV (type the URL into the Silk browser). Completely free, nothing to install on the viewing device.

• Live screen + system audio to any browser on the same network — no app, no account, no cloud.
• Fire TV friendly: works in the Silk browser, controllable with the TV remote.
• Buffered playback for smoothness (a few seconds behind live, like YouTube), with an automatic plain-HTTP fallback for browsers where MediaSource won't attach.
• Movie mode: serve an MP4 directly to viewers — full quality, seekable, with sound.
• Honest status line: Broadcasting with sound · 1 watching · 2.5 Mb/s means data is genuinely flowing.

1. Download the latest Mac Screencast-<version>-arm64.dmg from the Releases page.
2. Open the .dmg and drag Mac Screencast into Applications.
3. First launch only — the build is unsigned, so macOS will warn you:
   • Right-click Mac Screencast.app → Open → Open.
   • If it's still blocked: System Settings → Privacy & Security → Open Anyway, or run:

     xattr -cr "/Applications/Mac Screencast.app"

4. Click ▶ Start Broadcasting and grant the Screen Recording permission when asked, then quit and reopen the app once.

• macOS (screen capture uses the macOS Screen Recording permission)
• Node.js 18+ (only to run from source or build the app)

npm install
npm start

npm run dist

This produces dist/Mac Screencast-<version>-arm64.dmg — a double-clickable, self-contained app. The build is unsigned, so on first launch right-click the app and choose Open.

1. The app shows your watch URL (e.g. http://192.168.178.80:8080).
2. Click ▶ Start Broadcasting. First time only: grant the macOS Screen Recording permission, then quit and reopen the app.
3. Open the URL on any device on the same Wi-Fi. Playback starts a few seconds behind live (it's buffered for smoothness, like YouTube).
4. Sound: press any key / tap / press OK on a TV remote once if it starts muted. The Mac's own speakers mute while broadcasting (checkbox).

Any device with a web browser can be a viewer — there's nothing to install on it. Make sure it's on the same Wi-Fi as the Mac, open its browser, and type the watch URL the app shows (e.g. http://192.168.178.80:8080), including the :8080 part.

• Fire TV / Firestick — open the Silk Browser (free from the Amazon Appstore under "Internet"), type the URL, and playback starts. Press OK on the remote once if it starts muted.
• Android TV / Google TV (Chromecast) — no browser comes preinstalled; install one from the Play Store (e.g. TV Bro), then open the URL.
• Smart TVs (Samsung, LG, ...) — use the TV's built-in web browser with the same URL.
• Game consoles — Xbox has Edge built in; PS4/PS5 can reach a browser via the user guide/manual link. Same URL.
• Phones, tablets, laptops — any browser (Safari, Chrome, Firefox), same URL.

Tip: for films, open http://<mac-ip>:8080/player on the TV instead and use Movie mode — full quality and seekable (see below).

For films, use the Movies section instead of broadcasting: pick an MP4, open the player link (.../player) on the viewing device — full quality, buffered, seekable, with sound. Convert MKV/AVI to MP4 with the free HandBrake.

Screen + system-audio capture → WebCodecs (H.264/AAC) → fragmented MP4 → a tiny local server that fans the stream out to viewers over WebSockets (MSE playback), with an automatic plain-HTTP fallback (/live.mp4) for browsers where MediaSource won't attach. The server caches each stream generation's init segment so viewers can join and leave freely without interrupting each other.

src/
├── main/ Electron main process: window, permissions, HTTP/WebSocket server
│ ├── main.js
│ ├── preload.js
│ └── server.js
├── renderer/ The Mac app UI: capture, WebCodecs encoding, muxing
│ ├── app.js
│ ├── encoder.js
│ ├── index.html
│ └── style.css
└── viewer/ What browsers on the network receive
 ├── view.html / view.js live stream player (MSE + fallback)
 └── player.html / player.js movie player

• Viewer stuck "Waiting for the Mac..." — check the Mac app's status line; it names the failing stage.
• "Screen capture is stuck" — a macOS quirk after rapid stop/start; wait ~10 s and press Start again (the app also self-heals mid-broadcast).
• macOS firewall prompt — allow it; viewers must reach the Mac over the network.
• DRM content (Netflix/Prime) — captures black; a macOS restriction affecting every tool.
• Closing the MacBook lid stops everything — macOS always sleeps a laptop on battery when the lid closes, and no app can prevent it. Keep the lid open while casting (the app keeps the Mac and its display awake by itself), or use clamshell mode: plugged into power with an external display.

Issues and pull requests are welcome. Keep changes small and describe how you tested them (which browser/device watched the stream).

MIT