The MediaPositionState dictionary's position property is used when calling the MediaSession method setPositionState() to provide the user agent with the current playback position, in seconds, of the currently-playing media. This information is then, in turn, used by the user agent to provide a user interface which displays media playback information to the viewer.

For example, a browser might use this information along with the position property and the navigator.mediaSession.playbackState, as well as the session's metadata to provide an integrated common user interface showing the currently playing media as well as standard pause, play, forward, reverse, and other controls.


let positionState = { position: timeInSeconds };

let duration = positionState.duration;


A floating-point value indicating the current playback position within the media currently being performed, in seconds. This value should always be zero or more.


In this example, a player for a non-standard media file format, written in JavaScript, uses setInterval() to establish a callback which fires once per second to refresh the position information by calling setPositionState(). If the media is still playing when the interval is fired, setPositionState() is called with an object that specifies the duration, playback rate, and position as reported by a myMedia object that describes the track being played.

If the media is not playing, clearInterval() is used to remove the interval handler.

let positionInterval = window.setInterval(() => {
  if (myMedia.isPlaying) {
      duration: myMedia.trackDurationInSeconds,
      playbackRate: myMedia.playbackRate,
      position: myMedia.trackPlayPositionInSeconds
  } else {
}, 1000);


Specification Status Comment
The definition of 'MediaPositionState.position' in that specification.
Draft Initial definition.