eSIM glossary: ICCID, EID, APN, SM-DP+ and other terms explained

This is a plain-English glossary of the words that come up when you buy, install and use a travel eSIM on iPhone. The ones you'll actually need most are data roaming (turn it on for the travel eSIM, off for your home line), validity (how long the plan lasts once it starts) and ICCID (the number support will ask for). Terms are grouped by when you're likely to meet them, and where a term shows up in the Cabin Mode app or in iPhone Settings, we say where.

The basics

eSIM. Short for embedded SIM. A SIM that's built into the phone and downloaded rather than inserted. It does the same job as a physical SIM card: identifies you to the network and holds the settings to connect. What is an eSIM has the long version.

Travel eSIM. A prepaid eSIM for a country or region you're visiting. Usually data only: no phone number, no calls, no SMS. Cabin Mode's plans are travel eSIMs.

Physical SIM (nano-SIM). The small plastic card that sits in a tray on the side of the phone. US iPhones from the 14 onwards don't have a tray. See which iPhones support eSIM.

eUICC. The chip inside the phone that stores eSIM profiles. You'll rarely see the word, but it's the "embedded" part of embedded SIM.

Profile. One eSIM, as stored on the phone. An iPhone can hold eight or more profiles and use two at once. When you "install an eSIM", you're downloading a profile. In iOS these appear as lines under Settings › Cellular.

Line. How iOS refers to each SIM or eSIM, whether physical or embedded. You give each one a label, such as "Home" and "Travel".

Dual SIM. Two active lines on one phone. On iPhone, both can receive calls and texts, but only one carries data at a time. Dual SIM on iPhone for travel explains how they divide the work.

Identifiers: the numbers support asks for

ICCID. Integrated Circuit Card Identifier. A long number, usually 19 or 20 digits, that identifies one specific SIM or eSIM profile. Each Cabin Mode eSIM has its own ICCID, shown in the app. It's the most useful number to give support. On the iPhone, it's listed per line in Settings › General › About.

EID. eUICC Identifier. A 32-digit number that identifies the eSIM chip in your phone. It's the phone's number, not the plan's. Find it in Settings › General › About. Occasionally a provider needs it to issue a profile for a specific phone.

IMEI. The phone's hardware identifier. Dual SIM iPhones have one per line. Carriers use it for unlocking and for blocking stolen phones. Not usually needed for a travel eSIM.

Installing: activation and provisioning

SM-DP+. Subscription Manager – Data Preparation. The server that holds your eSIM profile until your phone downloads it. You'll see its address in manual install details. It looks like a web address, for example smdp.example.com.

Activation code. The string that tells your phone which profile to download from which SM-DP+ server. It usually looks like LPA:1$smdp-address$MATCHING-ID. A QR code is just this string in scannable form.

QR code. The usual way eSIMs are shared. You scan it with the iPhone camera, or from Settings › Cellular › Add eSIM › Use QR Code, and the phone downloads the profile. You can't scan a QR code on the same screen you're viewing it on, which is why app-based install exists.

One-tap install. An app hands the profile details to iOS directly, so you tap Install instead of scanning or typing. Cabin Mode installs this way by default, with the QR code and manual details as fallbacks.

Manual install. Typing the SM-DP+ address and activation code into Settings › Cellular › Add eSIM › Enter Details Manually. The slowest route, but it works when the others don't.

One-download rule. A profile can generally be downloaded once. After it's installed, the QR code won't work again, and if you delete the eSIM, you can't reinstall it from the same code. That's a restriction of the eSIM standard, not any one provider. More here.

eSIM Quick Transfer. An iOS feature for moving an eSIM between iPhones. It works for carriers that support it, which usually means your home carrier, not travel eSIMs.

Connecting: networks and settings

Cellular data line. The line iOS uses for mobile data. Only one at a time. Set it in Settings › Cellular › Cellular Data (Mobile Data in some regions). Abroad, set it to the travel eSIM.

Data roaming. A per-line switch that allows data when the line is on a network other than its home network. A travel eSIM always connects to partner networks, so it needs Data Roaming on. Your home line should have it off abroad, which is what stops roaming charges. How to avoid roaming charges goes through each setting.

Roaming. Using a network other than your carrier's own. For your home line, roaming abroad is what triggers your carrier's international charges. For a travel eSIM, roaming onto local partners is simply how it works and is already paid for.

Allow Cellular Data Switching. An iOS setting that lets the phone use data from your other line when the data line's coverage is poor. Worth turning off abroad so data never falls back to your home line.

APN. Access Point Name. The gateway setting that tells the phone how to reach the internet through a carrier. Travel eSIMs usually set it automatically. If it's wrong, you get signal but no data. It's in Settings › Cellular › line › Cellular Data Network.

PDP Authentication Failure. An iOS error meaning the phone couldn't open a data connection, usually because of a wrong APN, a conflicting profile or a VPN. Troubleshooting checklist.

Network selection. Whether the phone picks a network automatically or you choose one. In Settings › Cellular › line › Network Selection. Manual selection helps when the phone keeps trying a network your eSIM can't use.

Network generation (4G, 5G, LTE). The type of mobile network. 5G is faster where it exists; 4G/LTE is everywhere else. Plans list which generations they support, and iPhone 12 and later support 5G.

Operator / partner network. The local mobile company your travel eSIM connects to. Cabin Mode shows it on the plan screen.

Personal Hotspot. Sharing your iPhone's mobile data with other devices over Wi-Fi, USB or Bluetooth. Also called tethering. It follows the cellular data line. Hotspot guide.

Plans: what you're buying

Plan / package. The data allowance and validity you buy, for example 10 GB for 30 days in Japan.

Validity. How long a plan lasts once it starts. In Cabin Mode, validity counts down continuously once the plan starts, whether you use data or not. When it ends, the line stops, even with data left.

Activation policy. When the validity starts. Most Cabin Mode plans start on the first network connection at the destination; a few start when the eSIM is installed. The plan screen says which.

Fixed-data plan. A set number of GB for a set number of days. Use it at any pace.

Daily plan. A set allowance per day, such as 1 GB a day. Once the day's allowance is used, speed drops until the reset. Often marketed as "unlimited". Unlimited vs fixed data compares them.

Throttling. Deliberately slowing a connection. On daily plans, it happens after the day's allowance. Speeds after throttling range from about 128 kbps to 2 Mbps depending on the plan.

Fair use policy (FUP). The rules an operator applies to stop a plan being used in ways it wasn't intended, such as unlimited plans used as home broadband. "FUP1Mbps" on a daily plan means you're slowed to 1 Mbps after the daily allowance.

Top-up. Adding data to an eSIM you already have. In Cabin Mode, top-ups go onto the same eSIM, so there's nothing to reinstall. A top-up can't revive a plan that has already expired.

Monthly plan. In Cabin Mode, an optional renewal on eligible 30-day lines: each month adds the plan's data and 30 more days to the same eSIM. Cancel any time in the app. Long stays.

Regional plan. One eSIM covering several countries, such as Europe or Southeast Asia. Always check the coverage list. Regional vs country eSIM.

Coverage list. The countries where a plan works. On regional plans, it can differ a lot between plans with similar names.

Usage lag. The delay between using data and seeing it in the app. Operators report usage periodically; in Cabin Mode it lags one to three hours.

Your phone: locks and compatibility

Carrier lock (SIM lock). A restriction that makes a phone work only with one carrier's SIMs and eSIMs. Check Settings › General › About › Carrier Lock: "No SIM restrictions" means unlocked. A locked iPhone can't use a travel eSIM.

Unlocked. Works with any carrier. Required for a travel eSIM.

eSIM-only. An iPhone with no physical SIM tray. All US iPhones from the 14 onwards, the iPhone Air everywhere, and the iPhone 17 and 18 Pro lines in 12 countries.

Carrier settings update. A small update from a carrier that adjusts network settings. iOS prompts for it in Settings › General › About.

Frequently asked questions

What is the ICCID on an eSIM?

The ICCID is the unique number of one SIM or eSIM profile, usually 19 or 20 digits. It identifies the plan, not the phone. You'll find it in your eSIM provider's app and per line in Settings › General › About.

What is the difference between EID and ICCID?

The EID identifies the eSIM chip in your phone, so it stays the same whatever plans you install. The ICCID identifies one specific eSIM profile, so each plan has its own.

What is an SM-DP+ address?

The address of the server your phone downloads the eSIM profile from. You only need it for manual installation, where you type it in along with the activation code.

What does APN mean on iPhone?

Access Point Name: the setting that tells your phone which gateway to use for mobile data. Travel eSIMs usually set it automatically. A wrong APN causes signal with no internet.

What does data roaming mean on an eSIM?

It allows a line to use data on networks other than its own. A travel eSIM needs Data Roaming on to work; your home line should have it off abroad to avoid charges.

What does eSIM validity mean?

How long a plan lasts once it starts, such as 7 or 30 days. It usually counts down continuously, and the plan stops at the end even if data is left.