With unlimited data Sims you can use as much as you want without having to worry about running out of data. They almost always come with unlimited minutes and texts too.
However, as most people don't tend to actually use much data each month, you can often save by looking at a virtually unlimited 100GB/month Sim instead.
Some unlimited Sims aren't always 'truly unlimited' as networks can apply their own limits which can prevent you from using as much as you might want. This can be done via a number of ways, including capping download speeds, also known as throttling. Another way is to prevent you from tethering, which is why you connect laptop/computer to your phone in order to connect to the internet.
You'll find unlimited data Sim plans from most of the UK's major networks, including: Vodafone, EE, O2, Three, Tesco Mobile, Smarty, iD Mobile, Giffgaff, Asda Mobile, Superdrug Mobile, Honest Mobile and Lycamobile.
As you can imagine, Sims that come with unlimited data are usually more expensive than Sims with a set amount of data. Currently, the cheapest unlimited Sim available costs £11.75 with iD Mobile.
You'd need to weigh up if you actually need unlimited data. In our most recent data usage poll, only 8% of our users reportedly used more than 10GB/month of data, so Sims with unlimited data are for those who really have a need for huge amounts of data.
In most cases, you'll be able to use your Sim abroad, but your provider will usually set a limit as to the amount of data you can use as part of its 'fair use policy'. For example, Vodafone is capped at 25GB/month. See our Cheap mobile and data roaming guide for more information.