Google’s Chrome browser has supported Picture in Picture mode since Chrome 70, but the company has continued to improve and iterate on the feature, supporting the hardware media keys on your keyboard since Chrome 74 for example.
Now Google is working on adding a new feature to the pop-up. Google developer François Beaufort has added a commit for a mute button in the Picture in Picture window, saying:
This CL adds a mute button in the Picture-in-Picture window that reflects the muted state of the video. If there is no audio track, mute button will be hidden. This button is working only if experimental blink feature MuteButton is enabled or if the Origin Trial with the same name is enabled.
The Mute button will be added to the Play/Pause button and Back to Tab button. It is not clear when the feature will hit the mainstream version of the browser, but I suspect it will not be too long.