The HTML muted attribute is a Boolean attribute used in media elements such as <video> and <audio>. When specified, it indicates that the audio output of the video should be muted by default. This means that when the webpage loads and the media begins to play, the sound will not play automatically unless the user unmutes it or the web developer programmatically changes the setting. This attribute is particularly useful for improving user experience on web pages with background videos or autoplay media content, as it avoids surprising the user with sudden audio. It's a simple, no-value attribute; merely including muted in the tag is sufficient to apply its effect. For instance, in a <video> tag, you would write <video muted> to mute the audio by default.