Thaumic Cast

Your browser, on your Sonos.

Any tab, any room. Free, lossless and local.

Download for WindowsDownload for MacDownload for LinuxDownloadView on GitHub

Windows 10 or 11, 64-bit · 3.5 MB · macOS 13 or later · Apple silicon or Intel · 4.5 MB · x64 · .deb, .rpm or AppImage · For Windows, macOS and Linux · All platforms and files
The extension works in Chrome, Edge, Brave and other browsers built on Chrome.

Thaumic Cast runs on your computer: Windows, macOS or Linux, with Chrome, Edge, Brave or another browser built on Chrome. Open thaumiccast.com/get there.

All downloads
  • No account
  • No ads
  • No trackers
  • No cloud in between

The tab’s own sound comes from wherever the site streams it. From your tab on, it never leaves your network.

Two pieces. One button.

Set it up once. After that it is a click.

Step 1

Install the app

It finds your speakers and serves them the audio, on Windows, macOS or Linux. Then it keeps quiet.

Desktop app
Step 2

Add the extension

Add it to your browser from the Chrome Web Store. A short tour finds the app and your rooms.

Extension
Step 3

Pick rooms, press Cast

Open a tab that is playing, choose a room or several, and press Cast. That is all of it.

Extension · try it

Thaumic Cast

Connected to the desktop app

Lamplight Waltz

The Harbour Quartet
Cast to

The popup, ready to cast.Pretend speakers: nothing plays, nothing is saved.

What it does, once it is going.

Different tabs. Different rooms.

Kitchen gets jazz. Office gets “focus”. Up to 10 casts at once, each to rooms of its own.

Different tabs to different rooms

Anything that plays in a tab.

If it plays in your browser, it can play in your rooms. Thaumic Cast is not particular about what the audio is, only about where it is going.

Cast your first tab
  • YouTube Music
  • Spotify web player
  • Bandcamp
  • Web radio
  • Lectures
  • The cricket

Several rooms, one song.

Choose the kitchen and the living room and they play in step as one Sonos group. Each room keeps its own volume, and every cast starts no louder than a limit you set.

Several rooms

Picture and sound in step.

Sonos speakers play a moment behind the browser. Video sync plays the page’s sound early by that amount, so lips and words arrive together. Turn it on in Settings. It works with the default quality, though not with every player.

Video sync

Sounds like the source.

Lossless by default: the audio reaches your speakers uncompressed. On a busy network, a lighter preset is one click away in Settings.

Quality presets

Cast the whole browser

On Windows 11, the app can capture your browser’s sound directly, which avoids the gaps tab capture can leave.

Browser-wide capture

For the computer in the cupboard

Thaumic Cast Server is the same machinery with the window taken off. Linux x64 and arm64, as a service, or in Docker with host networking.

Thaumic Cast Server

Saved sets

Keep the rooms you always choose together as a set, and cast to them in one go.

Saved sets

Every feature

Small, local and yours.

Why it works the way it does.

Read the privacy policySigning, checksums and permissions

  • A small app, on purpose.

    A Sonos speaker plays what it fetches for itself. The app gives it something to fetch: your tab’s audio, served from your own computer. That is how the sound stays lossless, plays in several rooms in step, and needs nothing in between.

  • Your network, start to finish.

    Your audio never leaves your network. From your tab it goes to your computer and then to your speakers.

  • No account.

    There is nobody to have an account with, so there is nothing to sign in to.

  • Nothing counting you.

    No analytics or advertising code in the extension or the app, and none on this site. No cookies, so no cookie banner.

  • Open, so you can check.

    Everything it does with your audio is in the code, under AGPL-3.0, for anyone to read.

Before you ask.

Is it really free?

Yes. There is no paid tier, no trial and nothing to upgrade to. It is open source, under AGPL-3.0.

Will it work with my speakers?

It works with Sonos speakers on your network, as long as UPnP is on in the Sonos app (Account › Legal and Privacy › Privacy & Security › Connection Security › UPnP). It is on by default. Speakers on the older S1 software have not been tested yet.

Do I need AirPlay?

No. Thaumic Cast talks to your speakers itself, so it works with Sonos speakers with or without AirPlay, from Windows, macOS or Linux.

Why does my computer warn me when I install it?

The app is not signed yet, so Windows and macOS ask before they open it. Signing is planned. Until then, the download page shows exactly what to click. On Windows 11, Smart App Control can block an unsigned app outright. If it does, run the app on another computer on your network, or Thaumic Cast Server on Linux, and enter its address in the extension’s Settings.

Does it work over the internet?

No, and on purpose. The app and your speakers need to be on the same network.

Which browsers?

Chrome, Edge, Brave and other browsers built on Chrome. Firefox and Safari cannot capture a tab’s sound for an extension, so they are not supported.

Is there a delay?

A short one. The speakers keep a little audio in hand so the sound does not break up, which suits music and radio. For films, video sync plays the page’s sound early to match.

Is it made by Sonos?

No. Thaumic Cast is an independent project, not affiliated with or endorsed by Sonos, Inc.

Give your speakers something to fetch.

Start with the app. The extension takes a minute after that.

Download for WindowsDownload for MacDownload for LinuxDownloadOther platforms

Thaumic Cast runs on your computer: Windows, macOS or Linux, with Chrome, Edge, Brave or another browser built on Chrome. Open thaumiccast.com/get there.

All downloads