What is an eSIM?

Your complete guide to the benefits, technology and future of eSIM for IoT.

Quick definition: an eSIM is a SIM card that uses a remote SIM provisioning platform and eUICC technology to update connectivity preferences and switch mobile network operator profiles over-the-air (OTA).

eSIMs are available in any form factor and provide the same functionality as conventional SIMs, with enhancements that enable:

  • Secure, over-the-air updates for remote provisioning and management of profiles using Remote SIM Provisioning (RSP) systems
  • Secure storage of multiple network profiles on eUICC SIMs


What’s the difference between an eSIM and an eUICC SIM? In short, nothing! The term eSIM and eUICC SIM are used interchangeably.

The eUICC standard marks a shift from physical to digital with its remote SIM provisioning capabilities.

When the GSMA released the eSIM standard, they envisaged that eUICC SIMs would primarily be in the form of soldered chips (such as the MFF2) or implemented within a system on a chip (SOC). For this reason, they used the term embedded SIM (eSIM) for the remote SIM provisioning architecture. However, eUICC SIMs can be any SIM form factor, removable or non-removable and is now widely recognised by the term eSIM.

The difference between eSIM and Multi-IMSI

Multi-IMSI SIMs were introduced to overcome the coverage challenges faced by global deployments, but there was no industry standard for how the SIMs were remotely updated. So in 2016, the GSMA released the first global specification for eSIM (Embedded Subscriber Identity Module) which standardises the remote SIM provisioning (RSP) of any mobile device. This has since been updated with the most recent standard released in 2020.

Both multi-IMSI SIMs and eSIMs can be in any form factor, store multiple IMSI profiles and enable the switching from one network to another, but there are some key differences:

Who owns and stores the profile data

Some network operators don’t provide IMSIs to third parties for security reasons but will supply eSIM network profiles to their partners. For some IoT deployments requiring specific MNO connectivity, this prohibits the use of a multi-IMSI solution where IMSIs are preloaded onto the SIM.

The switching process

Profiles supplied for a multi-IMSI solution can be preloaded onto the SIM as bootstraps for automatic rotation and then updated via SMS whereas eSIM profiles must be requested from the MNOs SM-DP or loaded into your own SM-DP at the point of switching.

Fallback options

eUICC SIMs don’t use automatic rotation of bootstrap profiles. Once switched, the new eUICC profile is the primary operator on the SIM and if configured, the SIM will fallback to another profile. This can result in the device being offline for up to 25 minutes before the fallback is activated.

Which form factors are eSIMs available in?

eSIMs are available in standard plastic SIM cards and embedded form factors:

Form Factor


2FF (Mini SIM)

25mm x 15mm x 0.76mm

3FF (Micro SIM)

15mm x 12mm x 0.76mm

4FF (Nano SIM)

12.3mm × 8.8mm × 0.67mm

MFF2 (Embedded, M2M SIM)

5mm x 6 mm x 0.9mm

USON-8 (Embedded SIM)

2mm x 2mm x 0.5mm

How does an eSIM work?

All eSIMs have eUICC software installed to enable remote provisioning and management of network profiles. eUICC empowers devices to independently interchange connectivity to achieve the highest levels of service and availability, the best rates for data, and uptime.

Eseye have developed a technically advanced eSIM connectivity solution that combines a self-owned SM-SR, SM-DP, a cloud abstraction layer and combined multi-IMSI and eUICC SIM technology. IoT devices can localise connection to different network operators by using a solution called eSIM localisation.

Every Eseye eSIM comes with two profiles: a bootstrap profile that’s administered on manufacture and a step 2 localisation profile which allows new profiles to be delivered over-the-air.

The eSIM step 2 profile can be triggered to collect or deliver a new profile from the SM-SR and SM-DP, which contain the profiles from the different network operators that can be used.

The modem will recognise the SIM card has changed and will then reload the profiles and reconnect to the network using those new parameters.

The difference between consumer eSIMs and IoT eSIMs

Consumer eSIMs and machine-to-machine (M2M) eSIMs, used in IoT applications, adhere to different GSMA standards for remote SIM provisioning. In both standards, the eSIMs play a pivotal role in storing and overseeing multiple network profiles on devices but the M2M standard (SGP.01/02) involves pushing the profiles to devices, whereas the consumer standard (SGP.21/22) enables users to pull profiles onto their devices.

In May 2023, the GSMA have released SGP.31/32: the Remote SIM Provisioning standard for IoT and is based on the simpler consumer RSP standard. It removes the requirement for complex integrations between providers and addresses the needs of constrained devices.

Benefits of an eSIM

The addition of eUICC to SIM technology offers a vast array of distinct advantages compared to traditional SIMs:

Greater flexibility over connectivity

For most IoT deployments, a single MNO doesn’t provide the flexibility to handle global installations and single SKU products, mobile devices, gaps in coverage, roaming restrictions, and changes in the commercial and service landscape in mobile telecommunications. With more than 130+ major international carriers and hardware manufacturers support the eSIM initiative you can create a blend of networks than suit your connectivity requirements and effortlessly switch between them without the need to swap physical SIMs.

Simplified supply chain

eSIMs enable IoT devices to be standardised for simplified production and development using a single stock-keeping unit (SKU). As a result, you will be able to track inventory, improve manufacturing efficiencies, and identify future profit opportunities if you want to enter new markets without having to worry about changing your processes to accommodate a new connectivity provider.

Easy setup

eSIMs by nature are embedded meaning there is no physical SIM. With an eSIM you can build the out-of-the-box connectivity configuration you need to deploy worldwide. This makes both manufacturing and deployment more streamlined and cost-efficient.

Improved security

eSIMs typically employ stronger authentication mechanisms.

The GSMA specification for remote provisioning and management of eSIM profiles involves secure cryptographic processes, reducing the risk of unauthorised access and SIM cloning and communication between the eSIM and the network is often encrypted, making it more challenging for attackers to intercept and manipulate data during transit.

By enabling the embedding of secure credentials directly into devices and sending of security updates/patches over-the-air, eSIMs enhance the overall security of the IoT ecosystem and ensure that embedded software remains up-to-date and resistant to emerging security threats.

Simplified regulatory compliance

How the data is collected and processed, and whether it adheres to the laws of the country in which it is gathered is critical for global deployments.

These data sovereignty rules differ from country to country and certain industries have more stringent regulations. Roaming SIMs require data to be backhauled back to the home network which can violate data sovereignty regulations.

Permanent roaming is also known for preventing the success of global IoT deployments, with recent restrictions imposed by country regulators or networks leading to extortionate charges for data usage and removal of devices from the network.

eSIMs can provide a solution for both data sovereignty and permanent roaming concerns by using local profiles.

Considering an eSIM for your IoT deployment?

Our AnyNet+ eSIM enables intelligent over-the-air switching between multiple network operators. Connectivity is entirely customisable meaning that your device estate can seamlessly switch to another network’s connectivity and access the best availability, anywhere, anytime using our intelligent IoT connectivity management platform.

Eseye’s AnyNet+ SIM is fully eUICC compliant and supports multiple MNO profiles to allow complete connectivity autonomy to switch networks while preserving multiple fallback bootstrap profiles.

Eseye founded the AnyNet Federation, a worldwide alliance of MNOs that helps to meet the needs of customers to deliver successful IoT projects globally with complete connectivity assurance. This enables us to offer a flexible, global connectivity approach with access to over 700 mobile networks in more than 190 countries.

Paul Marshall

Founder & CCO


Paul is one of Eseye’s co-founders. With a background in senior design engineering, Paul’s focus is on ensuring his development, operations and support teams deliver solutions that work faultlessly in the field.

Paul was co-founder of CompXs, with Ian Marsden, and developed the world’s first IEEE 802.15.4 radio. Before CompXs, Paul was in senior radio design at Philips.

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