TabDecks

DJ mixer for Chrome tab audio. Capture two tabs (one per deck) and mix them in a dedicated window: per-deck volume, 3-band EQ with kills, crossfader, timeshift transport (pause / scrub / varispeed / vinyl brake / stutter), and extensible insert FX.

Built with TypeScript, Svelte 5, WXT, and the Web Audio API. All processing is local — no network access, minimal permissions (tabCapture, activeTab, storage).

How it works

Click the TabDecks icon on a tab that plays audio and assign it to Deck A or B. The tab's audio is captured (the tab itself goes silent) and routed through the mixer window — the mixer is the only output.

Everything the tab has played gets buffered, so each deck is a timeshift transport: pause, scrub backward, varispeed, brake, and stutter over buffered history; after a song has played through once, the deck offers full track control (seek, cues, loops).

Install in Chrome

TabDecks isn't on the Chrome Web Store yet — install it as an unpacked extension:

1. Build the extension:

   npm install
   npm run build      # → .output/chrome-mv3

2. Open chrome://extensions in Chrome.
3. Enable Developer mode (toggle in the top-right corner).
4. Click Load unpacked and select the .output/chrome-mv3 folder.
5. Pin the TabDecks icon from the extensions toolbar menu for quick access.

After making changes, run npm run build again and click the reload icon on the TabDecks card in chrome://extensions.

Ableton Link sync (optional)

TabDecks can lock both decks' tempo and phase to an Ableton Link session (Ableton Live, other Link-enabled apps, or other TabDecks instances) via a small local native-messaging bridge (Carabiner). Link is not required for normal use — it's an additive sync source alongside TabDecks' own deck-to-deck sync.

Setup (one-time, after installing the extension above):

npm run link:install

This downloads the pinned Carabiner release into tools/link-bridge/bin/, writes a native-messaging host manifest (com.tabdecks.link), and registers it with Chrome (Windows: HKCU registry key; macOS/Linux: NativeMessagingHosts directory). The manifest is scoped to TabDecks' extension ID, which is fixed by the pinned key in wxt.config.ts — this only works against the build produced by npm run build / npm run chrome, not arbitrary dev builds with a different ID.

Using it:

1. Reload the TabDecks extension (chrome://extensions → reload).
2. Open the mixer window and click LINK in the routing panel.
3. The status dot turns green and shows peer count + BPM once connected to a Link session.
4. Optionally click USE AS MASTER to slave both decks' tempo/phase to the Link session clock.

If the bridge can't connect, the panel shows an error and a hint to re-run npm run link:install.

Uninstall:

npm run link:uninstall

Removes the registry key / manifest file. The downloaded Carabiner binary is left in tools/link-bridge/bin/ — delete it by hand if you want it gone too.

Honest limitations

• No seeking forward past "now" — capture is a live stream; the buffer only contains audio that already played, and cannot fill faster than realtime.
• Pausing a deck does not pause the source tab — you drift behind live (the buffer absorbs it); JUMP TO LIVE snaps back.
• No file downloads — the extension never extracts audio files from streaming sites.
• Ads and rebuffering get recorded — the buffer contains whatever the tab played.
• DRM audio (e.g. Spotify web) may capture as silence — YouTube works.

Development

npm install
npm run dev        # WXT dev mode
npm run build      # production build → .output/chrome-mv3
npm run chrome     # launch Chrome with the built extension + test-tone pages
npm run test       # vitest
npm run check      # svelte-check

See CLAUDE.md for the project map and docs/architecture.md for diagrams.