Simply put, it is a dongle or MiFi router device you will need to buy outright and upfront, with a SIM slot, into which you will put a data-only, mobile broadband SIM. Unlike contract mobile broadband where you will pay a flat monthly fee for a set amount of usage, PAYG mobile broadband involves buying and owning the dongle or MiFi device, sticking a special SIM in it and adding top-up (money) onto the SIM. As you use data, it will eat directly away at your top-up.
The advantage should be obvious to anyone who needs mobile broadband, but only needs it very rarely, or as a last-ditch backup when you can't get access to wifi, or leverage the data allowance of their mobile phone. There's more than one way to get mobile broadband on pay-as-you-go, though. Several ways, in fact. They are:
Specifically when it comes to PAYG mobile broadband, there are a few different scenarios where it may come in handy. Most of them, though, sit in the context of it forming some sort of backup or failsafe. After all, you can use your mobile phone as a mobile broadband hotspot in most cases. The need for PAYG mobile broadband in addition should be relatively rare.
That's also where the PAYG element is useful of course. A rarely used fallback service is not something you are going to want to be paying a flat monthly fee for. Those who might want PAYG mobile broadband will fall into one or more of the following categories:
As things stand, you'll only get PAYG mobile broadband from three of the UK's four network providers: O2, Vodafone and Three. (EE does not offer PAYG mobile broadband data as such, although it does offer 30-day and 90-day preloaded data-only SIMs.) There are many other providers of phones and SIMs in the UK, of course, but they do not run on their own networks, instead they piggyback on one of these four.
These network providers (rather than the many virtual network providers) tend to offer a far wider range of services than anyone else. That's why when it comes to something as specific as PAYG mobile broadband, you will only find it available with these four. See our mobile phone coverage guide for more info.
As outlined above, only O2, EE, Vodafone and Three offer preloaded data SIMs that you can use for mobile broadband and choose to top up when you want. Remember also, that for PAYG mobile broadband you will have to buy the device, either a dongle or MiFi router, outright, before putting a PAYG mobile data SIM into it. Depending on what level of functionality you need, this may cost you between £10 and £100.
The differences between PAYG mobile broadband and contract mobile broadband have little to do with the functionality. Both will get you online when you're out and about. It's the means of getting there and the reasons you may have for choosing one or the other that set them apart.
In cases where you were comparing like-for-like data usage with a contract mobile broadband deal, yes. It is. You get less data for your money. However, if your aim is only to use your mobile broadband once in a blue moon, a fallback in case of emergencies for example, you're going to be paying substantially less for a PAYG mobile broadband deal across the average year.
The speeds you will get from a specific provider will be the same 4G/5G speeds you should expect were you to take out a mobile or SIM deal with that same provider.