eSIM or roaming: how to decide before you travel

First question: is your plan covered for roaming where you're going?

This is what changes things the most, and what most people overlook.

If your mobile plan is from an EU country and you're travelling within the EU. You can usually use your plan's data at no extra cost, within the limits set by your contract. If it's a short trip and you don't use much data, you often don't need anything else. Plans from outside the EU don't have this rule: check what yours includes.
Anywhere your plan doesn't cover. This is where surprise bills appear. Every operator has its own terms and add-ons, and it's worth reading them carefully: the difference between having an add-on and not having one can be huge.

Don't rely on memory: log in to your operator's account and check what your plan says for that specific country. It's the only source that counts.

The destination. Where your plan includes roaming (within the EU, for an EU plan), it's usually enough. Elsewhere, you'll almost always need to choose.
The number of days. A weekend of light use gets by on very little. Three weeks working from your phone doesn't.
What you use it for. Maps, messaging and a bit of browsing use little. Video, video calls and uploading high-quality photos use a lot.
Whether you need your own number. To receive texts from your bank, for example. With a data eSIM you keep it: your SIM stays in the phone.
How many people are travelling with you. Sometimes it works out better for one person to have data and share the connection than to buy for everyone.

When to use your home operator's roaming and when to use an eSIM
Your trip	The sensible choice
A few days where your plan includes roaming, normal use	Your usual plan, if your contract covers it
Several weeks where your plan includes roaming, or heavy use	A data eSIM, so you don't use up your plan
Any trip your plan doesn't cover	A data eSIM, unless you have a roaming add-on you're happy with
Several countries on the same trip	A regional or global eSIM, a single installation
You need to make a lot of phone calls	Your usual line; the Glowi eSIM is data only

General criteria, not the terms of any particular operator: yours are in your contract.

A second line, just for internet, that installs on your phone without a physical card and sits alongside your usual one.

You keep your number. Calls and texts still come in on your usual SIM; WhatsApp and Telegram work because they run over data.
You buy it and it arrives by email, with a QR code. It installs in minutes, on Wi-Fi, before you travel.
The days start when you connect to a network at your destination, not when you buy or install it.
You know what you're paying from the start: the plan has a fixed price.

Leaving it until the airport. Installing an eSIM needs a connection; do it at home, on Wi-Fi.
Not checking your contract. Two people with the same operator can have different terms depending on their plan.
Forgetting data roaming. With the eSIM installed but data roaming off, there's no internet. It's the most common mistake.
Leaving data on for your home line when you don't want it used. Turn it off on that line and you're sorted.

Can I have both and decide when I'm there?

Yes, and it's the most relaxed option: you install the eSIM before you leave and choose which line uses data in the settings, whenever you like.

Will I still get texts from my bank?

Yes, as long as you leave your usual SIM in the phone and switched on for calls and texts.

Can I share the connection with another phone?

It depends on the plan and the country; check what your destination's page says before you count on it.

What if I run out of data halfway through the trip?

Plans from €2.95, delivered instantly by email with the QR code and instructions.