Ofcourse it uses bandwith. All data sent and received over the internet uses Bandwith, I can't believe you guys only think it's the updates. Yes, the updates use some bandwith, but all chat ingame also use bandwith. Every action you do gets sent to the servers, although this data is very, very small, it adds up after a while. In short: (almost?) everything you do on Runescape gets sent to the RS servers, and brings you back data. So yes, Runescape does use bandwith, but I'm not sure how much exactly. I could test it, but I don't have any programs installed atm.