:volume-locked

The :volume-locked CSS pseudo-class selector represents an element that is capable of making sound, such as <audio> or <video>, but the audio volume of the media element is currently "locked" by the user.

User agents may set media muted or volume values according to user preferences (e.g., remembering the last set value across sessions, on a per-site basis, or otherwise). An element that is :volume-locked cannot be muted, un-muted, or have its volume changed via JavaScript. The locked status is an operating system or user agent preference.

:volume-locked {
  /* ... */
}

:volume-locked {
  border: 5px solid green;
}

video:volume-locked {
  border: 5px solid aqua;
}