eSIM Glossary: APN, EID, SM-DP+, Roaming and More

eSIM instructions can read as if they were written for network engineers. Most of the jargon, though, boils down to a few simple ideas, and you only need each term at a particular moment of your trip. This glossary is arranged in that order: what you'll see while checking your phone, choosing a plan, installing it, arriving, and occasionally fixing something.

Terms you'll meet when checking your phone

eSIM

Short for embedded SIM. It's a SIM chip built into the phone that can hold downloadable profiles, so you can add a mobile plan without inserting a plastic card. If your phone shows an "Add eSIM" option in its mobile or SIM settings, it has one.

eSIM profile

The downloaded package that turns the chip into a working line: the plan's identity plus the settings it needs to connect. A phone can store several profiles, and each one appears as its own line in Settings that you can switch on or off.

EID

The eSIM chip's own identification number. Seeing an EID is a good sign your phone supports eSIM. On iPhone it's listed under Settings → General → About; on many Android phones it's in the About phone section, and dialling *#06# shows it on many models. You rarely need it for a travel eSIM.

IMEI

Your phone's serial number on mobile networks. It identifies the device, not the plan, and dialling *#06# displays it. Phones with two lines often show two IMEI numbers, one for each.

Unlocked

A carrier-unlocked phone accepts SIMs and eSIMs from any provider. Phones sold with some contracts are locked to one carrier until that carrier unlocks them, and a locked phone typically won't work with a travel eSIM. On iPhone, Settings → General → About → Carrier Lock should say "No SIM restrictions"; otherwise ask your carrier.

Dual SIM

Two active lines in one phone: a physical SIM plus an eSIM, or two eSIMs, depending on the model. For travel it means your home number stays on for calls and texts while the travel eSIM handles data. You choose which line is used for mobile data.

Terms you'll meet when choosing a plan

Data-only

A plan that includes mobile data but no phone number for regular calls or SMS. HelloSIM eSIMs are data-only: calls and messages go through apps such as WhatsApp, FaceTime or Telegram, and your usual number stays on your home SIM.

Validity

The number of days a plan lasts. With HelloSIM, validity starts when the eSIM first connects to a network at your destination, not when you buy or install it, so you can set it up well before you travel.

Country, regional and Global plans

A country plan covers one destination. A regional plan covers a group of countries, such as Europe, Asia Pacific or Latin America. A Global plan covers many destinations across several regions. Plans differ by the amount of data and the number of days.

Top-up

Extra data added to an eSIM you already have. With HelloSIM, a top-up goes onto the same eSIM through the Check / Top up page, your account or the app, so there's nothing new to install.

Terms you'll meet when installing

QR code

The square barcode in your order email. Scanning it from the Add eSIM screen, or with the camera on some phones, points the phone to your profile and starts the download. It's meant for one installation, so keep it private, like a key.

SM-DP+ address

The address of the server where your eSIM profile waits to be downloaded. The name stands for Subscription Manager Data Preparation. You only type it in when installing manually instead of scanning; it's in your installation email together with the activation code.

Activation code

The unique code that identifies your particular profile on that server. Entered together with the SM-DP+ address, it lets you install the eSIM manually, which is handy if you're reading the email on the same phone and can't scan the QR code.

Terms you'll meet when you land

Network operator

The local mobile company whose masts your phone connects to. A travel eSIM uses partner operators at your destination, and the operator's name appears next to the line in Settings once you're connected. Each destination's plan page lists the networks it uses.

Roaming

Using a network other than your provider's own. Your home SIM roams when you go abroad, and your home carrier bills that under your tariff, often by the day or by usage. A travel eSIM also connects through partner networks, which is why your phone treats it as roaming too.

Data roaming

The phone setting that allows mobile data on a roaming network. Switch it on for the travel eSIM line, because the eSIM needs it to connect; with prepaid HelloSIM data, it adds no extra cost. Keep it off on your home line to avoid your home carrier's roaming charges.

4G / LTE

The mobile data standard behind most connections today. LTE is the technology's name, and phones display it as 4G or LTE. HelloSIM plans run on 4G/LTE in every destination sold, which is what most travel tasks, from maps to video calls, rely on.

5G

The newer generation of mobile networks. You'll only see it where the networks listed for a destination are marked 5G and your phone supports 5G. Everywhere else the phone simply uses 4G, with no action needed from you.

Terms you'll meet when something needs fixing

APN

Access Point Name: the setting that tells your phone how to reach the internet through the network. eSIM profiles normally set it automatically. Only change it if your installation instructions or the support team tell you to.

ICCID

The serial number of a SIM or eSIM profile. Each eSIM has its own, so it's one way of identifying a specific line, and support may ask for it. On iPhone you'll find it under Settings → General → About, listed for each line.

Network selection

Phones normally choose a network automatically. If your travel line shows no service, turning off automatic selection and picking one of the destination's listed networks by hand can help. On iPhone it's under Settings → Mobile Data → your travel line → Network Selection.

How the terms fit together

Put in order, the whole journey reads like this. You check that your phone has an EID and is unlocked. You choose a data-only country, regional or Global plan with the data and validity you need. The QR code, which contains the SM-DP+ address and activation code, installs the eSIM profile. On arrival, you switch on data roaming for that line, it connects to a local network operator over 4G or 5G, and the validity begins. If something stalls, network selection, the APN or the ICCID might come up in a chat with support at [email protected] or in the HelloSIM app.