Mobile broadband and SIM only run on the same mobile networks, but they solve different problems. Mobile broadband gets a device online where there is no fixed line. A SIM only deal covers the calls, texts and data on a phone you already own. This page explains both, and how the UK networks differ underneath.

Mobile broadband

Mobile broadband means using the mobile network for internet access instead of a phone line or fibre. It comes in a few shapes.

  • Dongles. A small USB stick that connects one device, usually a laptop. Cheap, simple, and increasingly rare.
  • Portable hotspots. Often called MiFi. A battery-powered box that creates a small wifi network for several devices at once. Useful for travelling, camping and building sites.
  • 5G home broadband. A router that sits by a window and serves a whole house over wifi, exactly like a fixed connection. This is the fastest growing option and the one most likely to replace a landline.
  • Built-in SIM slots. Some tablets and laptops take a SIM directly, with no extra hardware.

When mobile beats a fixed line

Mobile makes sense if the fixed options at your address are poor, if you rent and move often, or if you need something working today rather than after an engineer visit. Setup is usually a matter of plugging the router in. There is no installation appointment and often no long contract.

It is less suited to heavy, steady use by a full household. Speeds depend on how far you are from the mast and how many other people are using it, so the same router can feel quick in the morning and slow in the evening. If you work from home on video calls, a fixed connection is still the safer choice where one is available.

SIM only

A SIM only deal gives you calls, texts and data without paying for a handset. Because there is no phone to spread across the term, the monthly price is a lot lower than a contract that includes one. If your current phone works and is paid off, this is almost always the cheaper route.

Two contract lengths dominate. Rolling monthly deals let you leave with 30 days notice and change price when the market does. Twelve month deals cost less per month and lock the rate in. Keeping your existing number is straightforward either way: ask your current provider for a PAC code and give it to the new one.

The UK networks

Almost every mobile deal sold in the UK runs on one of three physical networks. Everything else is a brand renting space on top.

  • EE, owned by BT Group.
  • VodafoneThree, formed when Vodafone and Three completed their merger in May 2025. The two networks are still being combined, so coverage in a given area may come from either side for some time yet.
  • Virgin Media O2, which runs the O2 network.

The smaller brands, known as virtual operators, buy access wholesale and sell it under their own name. giffgaff, Tesco Mobile and Sky Mobile run on O2. SMARTY and iD Mobile run on Three. VOXI, Lebara and Talkmobile run on Vodafone. They are often cheaper than the network they sit on, and the coverage is the same, though some limit speeds or deprioritise traffic at busy times.

This matters more than the brand on the bill. If a network is weak where you live, every provider using it will be weak there too. Check coverage at your own postcode and, if you can, at your workplace before signing anything.

What to check before you buy

  • Coverage at the addresses you actually use, not just the headline map.
  • Whether the data allowance is genuinely unlimited or slows after a threshold.
  • What happens to the price mid-contract, which since January 2025 has to be stated in pounds and pence before you sign. Our guide to broadband and mobile price rises covers how that works.
  • Roaming charges, which returned to most UK networks after Brexit and vary widely.
  • For mobile broadband, whether the router is included or bought outright.

We are building out mobile broadband and SIM only comparison here. In the meantime, our broadband deals and provider reviews cover the fixed line side, including the providers that sell both.