Bandwidth caps are all the rage these days, in North America and around the world. We're talking about the notorious ceilings on how much broadband data you can use before your ISP starts charging you extra, or slowing down your connection, or shaping your traffic use (eg, blocking your access to certain applications).

AT&T's shiny new caps started on May 2: 150GB a month for DSL and 250GB for UVerse. AT&T customers will get a $10 charge if they cross the line, with that ding repeated for every 50GB thereafter. Comcast set a 250GB cap in 2008. Canadian ISPs have had them for a while, too.

Ars readers sometimes write in asking us how they can monitor their bandwidth use to avoid extra charges. Here are some links and pictures from major ISPs, which are broadly representative of the tools used by most Internet providers.

USA

AT&T offers a monitoring site here. Login with your user name and password, and you'll get a report like this.

This is from the AT&T DSL account retained at my end of the Ars Orbiting HQ. Our typical monthly usage has averaged out to 43GB a month over the last four. That includes plenty of Apple TV Netflix viewing, Skype video conferencing, Pandora listening, and YouTubing on top of the usual low bandwidth consuming activities, like website viewing and e-mail.

Comcast has a similar meter, which offers the same basic features: the metric for your cap (250GB), how much of the allotment you have used, and how much you have left to consume.

Canada, UK, Australia

If you are a Rogers Cable customer in Canada, you've got to log into your account, register, and then you can track your usage on a fairly detailed basis (at least according to the instructions), including use by day.

The process is similar for the United Kingdom's BT broadband service. Log in here. Go to "manage your services," hit the "broadband" tab, click "view your broadband usage," and you'll see something like this:

Needless to say, there are too many ISP services around the world for us to document. Last on our tour is Australia's BigPond ISP. Instructions here. And here's what the monitor looks like: