Yes. The Fluxer desktop app shares sound when you share your screen on Windows, macOS and Linux, and in the web app it depends on your browser.
What sound does the desktop app share?
On Windows and macOS, sharing an app window shares only that window's sound, and you can turn on "Capture entire system audio" in "Stream settings" to share all the sound on your computer. When you share a whole screen on Windows, "Playback devices" in the same menu lets you choose which of your playback devices the sound comes from.
On Linux, the desktop app uses PipeWire and lets you pick the apps whose sound you share. On Wayland, your desktop's own picker opens when you choose a screen or window, and you then pick the sound in "Stream settings" in the Fluxer app.
Can I share audio from the web app?
It depends on your browser. Chrome and Edge can share the sound from a browser tab, and on Windows they can also share your computer's sound when you share your whole screen. Firefox and Safari can't share sound with your screen, but the desktop app can.
Why doesn't my stream have sound?
First check that "Share stream audio" is on in "Stream settings". If you share an app window and the sound comes from another app, turn on "Capture entire system audio". On Windows, the desktop app can't capture some fullscreen games, and when you stream a camera or a virtual camera, its sound comes from the input you choose under "Audio device".
What quality can I stream at?
Free accounts and Plutonium have different resolution and frame rate limits for screen sharing and camera, and the Plutonium page shows them. In peer-to-peer calls, where they're available, everyone can stream at up to 4K and 60 fps for free.