I don't have any stats, especially not for hourly usage, but I have run Roll20 over my phone before, and it didn't use that much data at all. If you're not using Roll20 for voice or video, the biggest data usage will be images, which should only be downloaded ONCE per session. Beyond that, there will be the HTML/JavaScript to download, and data will be sent to update to update positions/create new objects (like tokens), but the amount of data used by those processes will be low. Also, keep in mind that even if you're not actively doing other things on the Internet, you computer might, such as downloading software updates. If your OS supports it, be sure to mark the connection as "metered" , which should cut down on background usage. I've got a game I'm playing in a few hours; I'll try to gather data from that, but it won't be the cleanest.