Hotel Wi-Fi or mobile data: which to use for what

The real question is whose network it is

The weak point of hotel Wi-Fi is not the hotel, it is not knowing for sure that you are on the hotel's network. The UK's National Cyber Security Centre puts it plainly: with public hotspots in hotels or cafés, there is no easy way to find out who controls the hotspot, or to prove it belongs to who you think it does.

CISA describes the trick that exploits this, the evil twin: someone copies the name of a public network and broadcasts a stronger signal, phones join it, and everything they send passes through the attacker's equipment. The defence is simple and takes a minute at reception. Ask for the exact network name and how the login works, and only join that one. A network called Hotel Free WiFi next to one with the hotel's real name is a reason to ask, not to guess.

Encryption has changed the picture

Public Wi-Fi is less risky than it used to be. The FTC notes that most websites now use encryption, so connecting through a public network is usually safe, and that the majority of apps encrypt their traffic too. The lock or https in the address bar is the sign to look for, in the phone's browser as well.

Two caveats keep this from being a free pass. Scam sites can be encrypted as well, the FTC warns, so the lock tells you the connection is private, not that the site is honest. And networks with no password send traffic over the air without Wi-Fi encryption; CISA's advice is to use networks with at least WPA2. Your iPhone can warn you when a network uses weak security, and Apple says it uses a rotating private Wi-Fi address by default on networks with weak or no security, which makes your phone harder to track across visits.

Mobile data comes with security built in

The NCSC's recommendation for working on the move is to avoid unknown hotspots and use your mobile network, which it describes as having built-in security, including when you share it with a laptop. CISA's travel tip card says the same in one line: using your mobile network connection is generally more secure than using a public wireless network.

Abroad, that is where a data eSIM fits. It gives you that mobile connection for the trip without roaming on your usual line, and because it is data only, WhatsApp and similar apps keep working with your own number. It has no number of its own, so codes sent by SMS still go to your usual line, which you can leave switched on for calls and texts. If the laptop needs a connection too, the hotspot guide covers sharing it.

Reliability: one connection for the whole building

Security is half the comparison; the other half is whether it works when you need it. A hotel's internet line is shared by every guest connected at the same time, so the speed you get depends on how many people are using it at that moment, and there is little you can do about it from your room. Many hotel networks also start with a login page, and the NCSC notes that VPNs can clash with these captive portals.

There is also an iPhone detail worth knowing. Connectivity Assist, the setting that uses mobile data when Wi-Fi is slow or unusable, does not work while the iPhone is roaming internationally, Apple says. Abroad, then, a poor hotel Wi-Fi will not be topped up automatically: if a page hangs, turn Wi-Fi off for a moment and let the mobile line take over.

A simple split for the trip

• Hotel Wi-Fi: downloading films and offline maps, photo backups, app and system updates, long video calls from the room.
• Mobile data: banking and payments, password resets and logins, anything you do in the street, and a laptop through the hotspot when you need to work.
• Either one: email and messaging in their official apps, kept up to date. The FTC notes that most apps encrypt their traffic.

Two settings help whichever you use. CISA advises turning off automatic connection to wireless networks, so the phone joins only the networks you choose. And the FTC's basic advice applies on the road too: keep the phone's system and apps up to date before you leave. If you need to size the data for the mobile half, the guide on how much data you need helps.