eSIM glossary

These are the words you meet when you buy and install a travel eSIM. Each one has a short meaning and what it changes for your trip.

APN

Access Point Name. The setting that tells your phone how to connect to the mobile network for data. Most travel eSIMs set it for you. If data does not work after you land, the provider's help page lists the APN to type in.

Activation code

A text code that installs an eSIM if you cannot scan the QR code. It starts with the SM-DP+ address (the provider's server) followed by a matching ID.

Carrier lock

A block some carriers put on phones they sell, so the phone only works with their SIMs. A locked phone cannot use a travel eSIM. On an iPhone, Settings, General, About shows "No SIM restrictions" when the phone is unlocked.

Data-only eSIM

An eSIM with mobile data but no local phone number. Most travel eSIMs are data-only. You can still call and message through WhatsApp, FaceTime or other apps.

Data roaming

Using mobile data outside your home network. A travel eSIM connects to local networks as a roaming partner, so you must turn data roaming on for the travel eSIM line. Leave it off for your home SIM to avoid charges.

Dual SIM

A phone that holds two lines at once, for example your home SIM for calls and texts plus a travel eSIM for data.

EID

The eSIM chip's own ID number, 32 digits long. A few providers ask for it. iPhones show it in Settings, General, About. Most Android phones show it under About phone.

eSIM

A SIM built into the phone as a chip. You download a plan to it instead of inserting a plastic card. One phone can store several eSIM plans and switch between them.

eUICC

The technical name for the chip that stores eSIM plans.

Fair use policy

Rules in an unlimited plan that slow your speed after a set amount of data in a day. Read it before you buy an unlimited plan.

Hotspot

Sharing your phone's data with a laptop or another phone over Wi-Fi. Some travel eSIMs block it, so check before you buy if you need it.

Local network

The mobile network in the country you visit, such as NTT Docomo in Japan. A travel eSIM uses one or more of them, and coverage depends on which ones.

Regional eSIM

One plan that works in many countries, such as a plan for all of Europe. It costs less than buying a plan for each country.

Throttling

A slowdown of your data speed, usually after you use up the fast data in your plan or hit a fair use limit.

Top-up

Adding more data to the eSIM you already installed, in the provider's app. You do not need to install a new eSIM.

Validity

How many days a plan lasts. Most start counting when the eSIM first connects to a network in the country you visit. Some start when you install it, so check your plan.

VPN

Virtual private network. An app that sends your traffic through a secure server. It protects you on hotel and cafe Wi-Fi, and in countries such as China it is the way to reach blocked apps on Wi-Fi.

5G

The newest mobile network generation, faster than 4G. Your phone, the eSIM plan and the local network all need to support it.

Ready to set one up? Follow the steps in how to install an eSIM.