Features
It plays your browser on your Sonos. Here is everything else. The pictures are the apps’ own parts, and the ones marked “try it” work.
YouTube Music, the Spotify web player, Bandcamp, web radio, a lecture, the cricket. Open the extension on the tab, choose rooms, press Cast.
Cast your first tabChoose 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.
Cast to several roomsExtension · try it: a cast in two rooms
Pretend speakers: nothing plays, nothing is saved.
Kitchen gets jazz. Office gets “focus”. Up to 10 casts at once, each to rooms of its own.
Different tabs, different roomsLossless by default: the Luxurious preset sends your speakers uncompressed PCM. On a busy network, a lighter preset is one click away in the extension’s Settings.
Advanced audio settingsExtension settings · try it: the quality presets
Pretend speakers: nothing plays, nothing is saved.
Video sync plays the page’s sound early by as much as the speakers play late, inside the site’s own player, with a fine-tune for each room. Tried on YouTube, Netflix and Prime Video. Turn it on in Settings. It needs a PCM cast (the default), and some players cannot be synced.
Video syncExtension · try it: the Video sync row
Pretend speakers: nothing plays, nothing is saved.
The desktop app lists each room, what it is casting and which rooms it is grouped with. Copy a cast’s URL to play it in a media player too, though not in time with the speakers.
The desktop appWindows 11 only: the desktop app captures your browser’s sound directly, which avoids the gaps tab capture can leave. It has to run on the same computer as the browser.
Keep the rooms you always choose together as a set. Rename or remove them in Settings.
Each room starts no louder than your limit, however loud someone left it. The limit is 30 unless you change it.
Your browser slows a silent tab, and a slowed tab sends audio late. This also plays the tab on your computer, too quietly to hear, so it stays awake.
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.
No account, no cloud, no trackers. Your audio never leaves your network.
The source for all of it is on GitHub.
Start with the app. The extension takes a minute after that.
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.