Even with so called unlimited broadband deals, fair usage policies are very common and apply to nearly all services. Different plans differ in their application of fair usage (or “fair use”) policies, but generally there will be a monthly or weekly threshold for download limits, which if you cross multiple times in a short period you will be judged to have infringed on the fair use policy and will have your broadband service limited in some way, whether by capping how much you can use per day or throttling the connection speed (limiting it to a much lower speed like 56kbps) for either the whole day or peak times.
The more information you get from your Internet Service Provider (ISP) the better in this regard, especially if you plan on doing a lot of downloading, since policies vary from ISP to ISP. In general though, most packages (including many of those labelled “unlimited”) will have a monthly cap of around 100GB of downloads, although this can vary wildly.
Vodafone for example have a 300GB per month fair usage policy but this is only used as a benchmark for which they will contact you to enquire if you are intending to make those downloads (to avoid viruses using your broadband). If you give them the all-clear then they lift the restriction. Sky were the first provider to offer “truly unlimited” downloads with no cap in 2008.
Mobile broadband users in particular need to be wary of download limits, even when a plan is labelled as unlimited there can there are normally lower fair usage caps per month than with terrestrial broadband, sometimes as low as 15GB. The “fair usage” intended by these plans means that they consider the service unlimited as long as you stick to normal internet usage like browsing and communication. With the advent of 4G, it can be quite easy to go over 15GB in a month by streaming high-quality video.
For mobile broadband, heavy usage at peak times can also put you at greater risk of setting of the fair usage policy limit.
In any case, you should check the terms and conditions if you think you may end up going over the fair usage limit. If still in doubt, contact an ISP representative and they should be able to give more information.
In some cases the ISP will contact you and give a warning if they see a pattern of what they consider heavy data usage. If the heavy usage persists, they will either throttle or cap you usage for a period. If this happens multiple times they may consider terminating the service. It is therefore quite avoidable, and in some cases if you justify your usage as personal you can reach an agreement.
Note that some users of some services may be hit with limits sooner, however, especially in the case of mobile broadband.
Many consumers are justifiably skeptical of the term unlimited broadband since it is often far from that. For example, downloading a high definition movie over your mobile broadband once every 3 days would put you over a 15GB limit, and watching a couple of movies a week would not be considered unreasonable or unfair.
On the other end of the spectrum, however, someone running a professional file-sharing setup (such as some users making money from Steam games) maxing out their broadband for nearly 24 hours a day could be considered as taking advantage of an offering aimed at conventional consumption.
This makes more sense when you consider the way broadband works. The contention ratio refers to the amount of users that share one line and can be quite high. Since one user downloading a lot especially at peak times will limit the amount of bandwidth available to other users, the ISP groups users based on their downloading patterns and allocates peak time bandwidth accordingly.
Since it can impact other users it is easy to see why fair usage policies can be sensible. In any event, if you consult your ISP before starting the contract then you can be sure the service is for you and what way it should be used then you can be sure it meets your needs and you can use it hassle-free.