eSIM, eUICC and MFF2, what each actually means
The three terms get used interchangeably across data sheets, procurement docs and sales conversations, and they mean three different things. This is the short version, in plain language, with a comparison table you can copy into a spec.
eSIM
(embedded SIM)In everyday use: a SIM that is soldered into the device rather than a removable card. There is no tray to open and no chip to swap.
More precisely: the word is used loosely. Sometimes it means the form factor (soldered rather than plastic). Sometimes it means the provisioning method (a profile that can be downloaded over the air instead of a fixed one). Most consumer and industrial documentation conflates the two, which is why the confusion started.
eUICC
(embedded Universal Integrated Circuit Card)In everyday use: the software on a SIM that lets it hold more than one operator profile and switch between them. It is what makes Remote SIM Provisioning (RSP) work.
More precisely: eUICC is a spec, published by the GSMA, that defines how a SIM stores multiple profiles, protects them, and lets an authorised platform push a new one or activate one already loaded. The chip a eUICC runs on can be soldered (MFF2) or removable — the software does not care.
MFF2
(also "M2M form factor")In everyday use: the physical shape of a soldered SIM chip — the little rectangular component you see on an IoT module board.
More precisely: MFF2 defines a specific footprint and pinout so any MFF2 chip fits any MFF2 pad. It says nothing about the software running inside. An MFF2 chip may or may not be eUICC-capable; you have to check the datasheet.
SGP.22 and SGP.32
(GSMA Remote SIM Provisioning specs)In everyday use: the two GSMA specifications that define how new operator profiles get onto a SIM after it has been manufactured. SGP.22 is the consumer version, used when someone scans a QR code on a phone to add an eSIM plan. SGP.32 is the newer IoT version, designed so unattended devices can receive and switch profiles without a person present.
More precisely: both are Remote SIM Provisioning (RSP) architectures published by the GSMA, layered on top of eUICC. SGP.22 assumes a device with a screen and a user, so profile download runs against a Local Profile Assistant (LPA) inside the OS. SGP.32 introduces an eSIM IoT Manager (eIM) that orchestrates profile download remotely, and an IoT Profile Assistant (IPA) that runs alongside the eUICC, together allowing a fleet of headless devices to be managed under remote control.
Why it matters for IoT: SGP.32 is the specification the industrial and IoT world has been waiting for. Every device connected to SIMSY benefits from the flexibility and control that SGP.32 delivers, from over-the-air profile changes at scale to consistent lifecycle management across a global estate.
Summary of the key SIM terms
| Term | Category | Governs | Governed by |
|---|---|---|---|
| eSIM | Common name | How it is packaged and provisioned (loosely) | Marketing convention |
| eUICC | Software spec | How profiles are held and switched over the air | GSMA |
| MFF2 | Form factor | The physical footprint and pinout of a soldered chip | JEDEC / GSMA |
| SGP.22 | Provisioning spec | Consumer RSP: profile download via a Local Profile Assistant on a user device | GSMA |
| SGP.32 | Provisioning spec | IoT RSP: profile download to headless devices via an eIM and IPA | GSMA |
The common combination behind "eSIM in an IoT device" is an MFF2 chip running eUICC software, provisioned with an operator profile. Say all three when you want to be unambiguous.
The questions people ask next
Is eSIM the same as eUICC?
No. eSIM commonly refers to a SIM soldered into the device — a form factor with no removable card. eUICC is software on the SIM that lets it hold more than one operator profile and switch between them. A SIM can be one without the other: some MFF2 chips are not eUICC-capable, and some plastic SIMs are.
Is MFF2 the same as eSIM?
Not quite. MFF2 (also called M2M form factor) is the physical shape and pinout of a soldered SIM chip. eSIM in common usage means "soldered, remotely provisioned", which is usually MFF2 hardware running eUICC software. People say eSIM when they mean any of the three things separately.
Do I need eUICC to change operators over the air?
Yes. Remote SIM Provisioning (RSP) — the process behind downloading a new profile without swapping the card — depends on eUICC software on the SIM. Without it the SIM holds a single profile fixed at manufacture.
Which one do I actually order?
For most connected-device deployments: an MFF2 soldered SIM with eUICC software, so the device has no removable card and you can change profiles over the air later. For phones and consumer eSIM, the same combination applies but is buried under "eSIM" as a marketing term.
Are you selling me a chip or a profile?
When you buy an eSIM in the SIMSY shop, you are buying a profile — an activation code that installs a SIMSY profile onto an existing eUICC-capable SIM in your device. The physical chip is manufactured separately, by the device maker or by us in the physical SIMs we ship.
Still untangling the vocabulary?
The full terminology page groups every commonly-confused term with the same treatment as this one, so a supplier catalogue reads the same on Monday as it does on Friday.