What is an eSIM? Profile and eUICC

An eSIM is a profile, not a chip

An eSIM is the operator profile stored on an eUICC, the secure element soldered into the device or supplied in a removable package. The chip is hardware. The profile is subscription data: credentials, IMSI and network parameters. One eUICC can hold several profiles. A device enables the profile it uses, and SGP.22 v3.0 adds multiple enabled profiles for devices that support them.

The chip carries a 32-digit EID that identifies the hardware. Each profile carries an ICCID that identifies the subscription container. Download a new profile and the EID stays the same while the ICCID changes. An inventory that records only ICCIDs cannot say which chip a profile sits on, so record both.

The specification follows who is present

The specification follows the activation, not the shape of the hardware. Consumer devices use SGP.22. A person scans a QR code or opens an app, the local profile assistant downloads the profile, and the person confirms it. Unattended fleets use SGP.32. An eSIM IoT manager in the backend selects the profile, and an IoT profile assistant on the device executes the download with no screen and no one on site.

A soldered eUICC can run a consumer flow if the device has a screen and a user. A removable eUICC can run an IoT flow if the module and the management platform support SGP.32. Older M2M estates may still run SGP.02, and that hardware cannot become SGP.32 over the air.

How a profile reaches the chip

In the consumer flow, a profile provider prepares the profile on an SM-DP+ and gives the user an activation code, usually as a QR code. The device's local profile assistant connects to the SM-DP+, downloads the profile, installs it on the eUICC and enables it after the user confirms. A discovery server can also tell the device that a profile is waiting. The exchange runs over an IP connection, usually Wi-Fi or the device's existing mobile data.

In the IoT flow, the eSIM IoT manager triggers the download and the IoT profile assistant executes it. The device needs a bootstrap connection first: a bootstrap profile, a local network or another temporary path. Without that connection the profile cannot arrive, and the device stays offline. Plan the bootstrap before the device is sealed in the field, and test the download on the real hardware.

What an eSIM does not change

An eSIM does not change the IMSI, the MSISDN or the market's rules. The IMSI still identifies the subscription, the MSISDN is still the diallable number, and the destination market still decides whether the device and the subscription may be used there. An eSIM does not create coverage, bypass roaming rules or make a foreign subscription local. It changes how the profile arrives, not what the profile may do.

It also does not encrypt user traffic. The profile is protected in transit and at rest by the remote-provisioning architecture. The data the device sends is protected by the application and the network, not by the SIM form. If the traffic needs encryption, run it end to end.

Physical, embedded and soldered

Three forms matter in practice. The removable plastic SIM is the familiar card and still common in devices with a slot. The eUICC can also be supplied in a removable form factor, which keeps a service visit possible. The soldered eUICC is fixed to the board and cannot be lost or swapped, which suits devices that must survive vibration, heat or tampering. The form decides the logistics: a removable card can ship separately, while a soldered eUICC must be provisioned after assembly, with the profile plan ready before the device leaves the line.