Mobile data versus Wi‑Fi

Traditional telephones use wires and a network of exchanges to connect subscribers around the world. Any subscriber can call another by dialling their number. In return for this convenience and to pay for the upkeep of the infrastructure, telecoms companies charge for calls, usually by the minute.

Mobile phones partly replace wires with radio waves. The land is divided into cells by a network of towers with which nearby phones communicate. The practice of charging by the minute remains, though many subscriptions offer a monthly quota of minutes for a fixed price that can work out better value.

Mobile data

In the nineties, second generation or 2G technology made Internet access possible via these radio waves, bringing websites and email to mobile phones. Things really took off a decade later with smartphones and faster 3G and 4G technology. Charging for this mobile data by the minute didn’t make sense, as it was to occur in frequent but intermittent and often very short bursts.

Instead, mobile data use is charged by the megabyte. In other words, you pay for the quantity of information you exchange, irrespective of when or for how long you do so. This is logical for the telecoms companies, for technical reasons, but makes it harder for customers to comprehend what they’re using. If your subscription includes 4 GB (4,000 megabytes) of data per month, what does that mean in practice?

An email might be 20 kilobytes (thousandths of a megabyte) while a web page might be 500 kilobytes – half a megabyte – and a photo around two megabytes. But these are estimates or averages. The point is, you can’t easily count what you use, like you can with minutes.

To complicate things, smartphones use mobile data for much more than just websites and email. How much your iPhone uses when you get driving directions or ask Siri if it’ll rain tomorrow is anyone’s guess. And some usage happens ‘in the background’—like while your phone is idle in your pocket or by your bed. It receives emails, updates apps, checks its location, keeps its clock accurate and does other things you might not think about.

Over time you may become familiar with how your typical mobile Internet use translates into megabytes. To help, smartphones keep a count of how many megabytes you use—you can usually find this in the settings app. Your provider (e.g. Vodafone or EE) also counts your data use, which you can see by logging into their app or website.

It’s also worth finding out what will happen when you reach your monthly quota. Does your provider prevent you exceeding it, or start charging by the megabyte for excess use? (And if so, how much? It may be surprisingly high.)


Another development of the nineties, Wi‑Fi also offers wireless Internet via radio waves, but over much shorter distances—on the order of metres. It tends to be available where a landline broadband subscription is shared among laptops within a building or campus, but smartphones can use it too.

Because it extends an existing broadband service, Wi‑Fi in homes, offices and universities is free and rarely has a monthly limit. In hotels, railway stations and other commercial environments, Wi‑Fi is often free, though some places may charge a small amount. Such a fee is made clear when you first connect, so you can choose whether to proceed; the money can’t be taken automatically.

In any case, Wi‑Fi is a great alternative to mobile data.

Note that you must explicitly ‘join’ your phone to a particular Wi‑Fi network. But then, for as long as you remain in range, it will favour that Wi‑Fi over mobile data. So you’re free to visit loads of websites – and even do data-intensive tasks, like watching videos – without worrying about your mobile data allowance.

Privacy and security

When you use Wi‑Fi out and about, you’re putting a level of trust in whoever operates it. It’s possible to have rogue networks that, for example, capture information you send. In some cases it may even be possible for anyone else in the vicinity to eavesdrop on what you are doing.

The safest place to use Wi‑Fi is usually at home: your network has a password known only to you and your family – and guests you choose – and you trust your router because it’s connected directly to your broadband provider.