What Is an eSIM Card and How Does It Work? Chips, Profiles and Activation

Short answer: an eSIM is a small chip soldered inside your phone. Instead of swapping cards, the phone downloads a digital “profile” from the mobile operator’s server. The profile holds the details a network needs to recognise you. A phone can store several profiles and switch between them in Settings.

This page explains the technology. If you just want to know what a travel eSIM is and whether you need one, start with our travel eSIM guide.

What is an eSIM card?

A SIM card does one job: it proves to a mobile network that you’re a paying customer. It holds an identity and the keys to authenticate it.

An eSIM does the same job, but the chip is built in and rewritable. The industry name for the chip is eUICC (embedded universal integrated circuit card). Because it’s rewritable, the identity can be downloaded over the internet instead of arriving on a plastic card.

The parts that make an eSIM work

Part	What it is	Where you see it
eUICC	The rewritable chip inside the phone	Nowhere; it’s soldered in
EID	The chip’s unique ID number	Settings > About (iPhone) or About phone (Android)
Profile	One operator’s identity and settings, downloaded to the chip	Each line in your SIM settings
ICCID	The ID number of a single profile	Under each line’s details
SM-DP+ server	The operator’s server that prepares and sends profiles	Part of the activation code
LPA	Software in the phone that downloads and manages profiles	The “Add eSIM” screens in Settings

These parts are defined by the GSMA, the mobile industry body, in its consumer eSIM specification, SGP.22. Every eSIM phone follows it, which is why a profile from one provider installs on any compatible phone.

What happens when you install an eSIM

1. You get an activation code. It’s shown as a QR code, a link, or a one-tap install button. It contains the SM-DP+ server address and a matching ID for your profile.
2. Your phone contacts the server. The LPA sends the code and the chip’s EID over Wi-Fi or mobile data.
3. The server sends an encrypted profile, locked to your chip so it can’t be copied to another phone.
4. The chip installs it. A new line appears in your SIM settings. You can label it, for example “Travel”.
5. The profile connects when it finds a network it’s allowed to use. For a travel eSIM, that’s a partner network at your destination.

Steps 2–4 usually take under a minute. Here are real-world activation timings.

QR code, one-tap install or carrier app: what’s the difference?

All three deliver the same activation code. Only the way you hand it to your phone changes:

Method	How it works	Catch
QR code	Scan it in Settings > Add eSIM	Needs a second screen or a printed code
One-tap install	Tap a button on the provider’s page; the phone opens the install screen	Must be done on the phone itself
Carrier or provider app	The app passes the code to the phone	One more app to download
Manual entry	Type the SM-DP+ address and activation code	Easy to mistype

BazTel uses one-tap install on both iPhone and Android, so there’s no QR code to scan.

How many eSIMs can a phone hold?

Several. Most recent phones can store multiple profiles and run two lines at once, for example your home number and a travel eSIM. The Pixel 11, for instance, stores up to eight eSIMs and runs two at a time.

Stored profiles that aren’t in use don’t connect or use battery. You can switch them on and off in Settings, or delete them when a trip ends.

How a travel eSIM connects abroad

A travel eSIM profile usually belongs to an operator in one country, with roaming deals in many others. When you land, your phone joins a local partner network, which recognises the profile and lets it connect.

Your data then often travels back to a hub before reaching the internet. That’s called home routing. A distant hub adds delay: in Ookla’s 2026 data, the same Japanese network showed 54 ms latency locally and 543 ms via Madrid. BazTel uses regional hubs: Hong Kong for Asia, Germany or Poland for Europe and the Middle East, and the US for the Americas.

Is an eSIM more secure than a SIM card?

In one way, yes: nobody can pull an eSIM out of a stolen phone and put it in another. Profiles are also encrypted and locked to the chip.

But an eSIM doesn’t stop SIM-swap fraud, where a criminal convinces your carrier to move your number to their device. That risk sits with your carrier account, not the chip. Here’s how SIM swap fraud works and how to prevent it.

What an eSIM can’t do

• Work on a locked phone with another operator’s profile. The phone must be unlocked.
• Move itself to a new phone. Some phones can transfer a profile; otherwise the provider reissues it. BazTel can reissue your eSIM, with remaining data, if you lose your phone.
• Work on phones sold in mainland China, which mostly don’t support eSIM. Check the eSIM compatibility list.

Frequently asked questions

How does an eSIM work?

A chip in your phone downloads a digital profile from the operator’s server. The profile tells the network who you are, so the phone can connect without a physical card.

What is an eSIM profile?

One operator’s identity and network settings, stored on your phone’s eSIM chip. Each profile appears as a separate line in your settings.

What is in an eSIM QR code?

The address of the operator’s profile server and a matching code for your profile. Scanning it tells your phone where to download the profile from.

Can I reuse an eSIM QR code?

Usually not. Most codes work once, because the profile is locked to the first phone that downloads it.

Does an eSIM use the internet to activate?

Installing needs a connection, usually Wi-Fi. After that, the profile connects to mobile networks like any SIM.

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