Xenon was one of the default notification tones shipped with Android 4.4 KitKat, the version of the mobile operating system released in 2013. Like other system sounds of that era, it was designed to be short, clear and easy to notice without being intrusive. As KitKat phones spread, the tone became familiar to millions of users, and it later circulated on soundboards and in editing libraries. Creators still reach for it today when they want an authentic mid-2010s Android alert rather than a modern default sound.