The Media Session API connects a player to controls outside the page: media keys, phone lock screens, Chrome 1 's media hub and smartwatches. Set navigator.mediaSession.metadata = new MediaMetadata({ title, artist, album, artwork }), register handlers such as setActionHandler('nexttrack', playNext), and call setPositionState({ duration, position }) so lock-screen scrubbers stay accurate. Wrap setActionHandler() in try: unknown actions throw TypeError (Chrome 152 accepts togglemicrophone and hangup for video calls but rejects voiceactivity). Firefox 555 for Android exposes the API without showing controls.