What Is an eSIM?

An eSIM is a SIM card that is already inside your phone. Instead of pushing a piece of plastic into a tray, you download a profile — a small file that tells the phone which network to join and proves you are allowed to. The hardware was soldered in at the factory; buying an eSIM buys you permission to use it.

That single change — plastic to download — is the whole story. Everything people find useful about eSIMs follows from it, and so does everything they find annoying. It is also not any one company’s feature: eSIM is an industry specification from the GSMA, the body operators use to agree on how phones and networks talk to each other.

You can buy a local data plan before you leave and switch to it when you land, instead of hunting for a shop at the airport or paying your home carrier’s roaming rate. Activation takes a couple of minutes on hotel wifi.

You also keep your normal number. Nearly every eSIM-capable phone can hold your home SIM and a travel eSIM at once, with the travel plan carrying data and your usual number still receiving calls and texts. That is the part most people actually want. Some recent models have no tray at all — Apple lists which iPhone and iPad models are eSIM only, and Google says the same of a US Pixel 10 — which changes nothing here except that both lines are then eSIMs.

A travel eSIM is almost always data only. It gives you an internet connection, not a phone number in the country you are visiting. Everything that runs over the internet works normally — maps, messaging, email, calls in WhatsApp or FaceTime. What does not work is anything that needs an SMS to a local number.

Most phones sold since about 2020 do, and the ones that do not are covered in which phones support eSIM. Rather than trust a compatibility list, though, check the phone itself — the answer is definitive and takes ten seconds:

• iPhone: Settings → General → About. If there is an Available SIM or EID entry, the phone has an eSIM.
• Android: Settings → Network & internet → SIMs → Add SIM. A "Set up an eSIM" option means yes — that is the wording in Google’s instructions for setting up a new eSIM.
• Either: dial *#06#. If an EID appears alongside the IMEI, the phone has eSIM hardware.

Two caveats the spec sheet will not tell you. A phone bought on contract may be carrier-locked, which blocks other networks whatever the hardware supports. And the market a phone was sold in matters: Apple states that in mainland China only the iPhone Air and iPhone 17e support eSIM at all, so an otherwise identical handset bought there will not take one.

1. 1Buy the plan. You get a QR code, usually by email, within a minute or two.
2. 2Scan it from the phone’s eSIM setup screen while on wifi. This downloads the profile.
3. 3Label the line something you will recognise later, like the country name.
4. 4On landing, turn the travel line on for data and leave your home line on for calls and texts. Turn data roaming on for the travel line — it is roaming from that network’s point of view, even though you are paying local rates.

Install before you fly, activate when you land. Almost every plan’s validity starts when the eSIM first connects to a network, not when you buy it, so installing early costs you nothing. The full walkthrough, including what to do when the code will not scan, is in how to install an eSIM.

Headline price is the wrong number. A $4 plan with 1 GB costs four times as much per gigabyte as an $8 plan with 5 GB, so price per GB is what makes plans of different sizes comparable. Then check the validity window, whether you can top up mid-trip, and — for anything advertised as unlimited — the daily cap after which speeds drop.

You can see every provider we track scored on exactly those terms by destination or by provider.