iTunes Match is Apple's subscription music locker service. It lets you compare your entire library with the iTunes music catalog. If it finds the same song, it lets you stream or download it from iTunes, to any of your Apple devices, immediately or for as long as you stay a subscriber. If it doesn't find the same song, it uploads your version and lets you stream it just the same. Because your music is always available on the iTunes servers, it works like a backup, making sure you don't lose your collection even if you lose your device. Because it streams, it also lets you keep your music "nearline" — not taking up precious storage space on your device, but available any time you can connect. So, how does iTunes Match work?