Soft SIM, eSIM and iSIM: What’s the difference?

Ian Marsden

Founder & CTO


In our increasingly connected world, IoT SIM cards play a vital role in enabling cellular communication. However, traditional physical SIM cards are now being replaced by eSIM, Soft SIM, and iSIM. These newer technology alternatives offer flexibility, convenience, and exciting possibilities for enterprises and manufacturers alike.

This blog post compares Soft SIM, eSIM and iSIM, and explores their features and benefits, as well as their advantages and disadvantages.

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:

eSIMs revolutionize connectivity and device design with their flexibility, security, and space-saving efficiency. Supporting over 130 international carriers, eSIMs enable seamless switching without the need for physical SIM swaps. Their space-saving feature, achieved by soldering the SIM onto the circuit board, eliminates the need for physical SIM slots, allowing for more compact device designs or additional internal space.

Security is enhanced through soldering, and reduces the risk of physical tampering, but eSIMs also employ stronger authentication mechanisms than traditional SIMs. 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.

With eSIMs, costs are reduced with streamlined manufacturing processes, as eSIMs eliminate the time and expense associated with fitting traditional SIMs. Additionally, eSIMs offer increased durability and are less susceptible to physical damage or contact degradation compared to traditional SIMs that use gold-plated spring contacts.

The eSIM comes with little drawbacks.

Some MNOs and SIM resellers supply eSIMs as single IMSI (or single profile) SIM cards. Without Remote SIM Provisioning (RSP) technology, which enables profiles to be remotely managed, organizations IoT initiatives are still at risk of being subjected to future data sovereignty legislation and permanent roaming restrictions.

Soldering the eSIM onto the device can also present challenges when it comes to device disposal, but the positives of this feature far outweigh the negative for IoT use cases.

iSIM, or Integrated SIM, takes the concept of eSIM a step further by embedding the SIM card functionality directly into the modem chipset. This integration brings greater control and flexibility to device manufacturers, while maintaining the benefits of the eSIM technology.

iSIM technology offers significant advantages in device design, particularly in terms of size, power efficiency, and ruggedness. By consolidating the cellular modem and SIM into a System on Chip (SoC), iSIM dramatically reduces the footprint required for connectivity components. This size reduction, up to 98% smaller than eSIMs, opens new possibilities for IoT device designs, especially in applications where space is a critical factor.

Beyond size, iSIM SoCs contribute to improved power usage and device performance. The close integration of components enables more efficient operation, reducing energy consumption while delivering power more effectively to the SIM. This synergy results in a win-win situation for both power efficiency and overall device performance.

Furthermore, iSIM enhances device ruggedness by minimizing discrete components, reducing the risk of damage, particularly in outdoor and challenging environments. This feature makes iSIM-equipped devices more resilient to factors like water ingress, tampering, and adverse weather conditions. Overall, iSIM technology not only simplifies the supply chain and reduces costs in IoT deployments but also enhances hardware-based security, acting as a secure Root of Trust (RoT) for authentication and safeguarding sensitive data.

A potential disadvantage for some – but not all – iSIMs is if the reprogramming option was disabled. This would limit the ability to change mobile network provider and optimise connectivity.

Much like eSIM, another potential disadvantage is that because the iSIM cannot be removed, when the IoT device reaches the end of its life, it becomes difficult to dispose of the iSIM inside. From a billing perspective, this does not cause any issues as it is extremely easy to deactivate the SIM so that no further charges are incurred once the device is switched off.

Soft SIM, also known as virtual SIM or software SIM, is an entirely software-based method of storing and displaying subscriber identity information to modems.

Soft SIM offers advantages in two key areas. To identify the subscriber, soft SIM can be supplied as a file with the unique security and identity information enclosed. For users, this may be more convenient and promote easier device configuration.

Secondly, Soft SIM allows manufacturers to simplify supply chain processes as they can replace the need to physically handle and distribute SIM cards with a programming step during production.

Organisations planning to use soft SIMs for IoT deployments should exercise caution since it is an emerging, early-stage technology that comes with some inherent challenges. Notably, the GSMA has not approved the industry standardisation of Soft SIM. Because it has not been approved by a known regulatory body, it is not subject to regulation or held to industry standards. Furthermore, without regulatory body assurance, the technology may present interoperability challenges due to different implementation approaches and fail to reach mass adoption like the eSIM and iSIM.

Another critical concern revolves around remote SIM provisioning (RSP), a protocol outlined by the GSMA for downloading SIM profiles. With Soft SIMs, the identity and security keys are provided by a file set run on the microcontroller, so the data can always be changed with firmware updates, either by local reprogramming or by downloading a new firmware image over-the-air.

This can present problems though. In the absence of regulatory oversight, Soft SIM lacks adherence to remote SIM provisioning standards which heightens security risks. Process data files should be unique and only used once because they contain the credentials that the device uses to authenticate the MNO. Soft SIM presents potential security vulnerabilities and the misuse of credentials if the unique information is in any way altered.

Finally, the GSMA emphasizes that secure elements based on certified hardware and software are crucial for robust SIM security. Soft SIM, lacking such certification, exposes IoT data to potential attacks, risking a loss of customer confidence in operator systems. Both operators and enterprises should beware of the threats inherent with soft SIM technology. Tier 1 operators are acutely aware of this risk and rarely enable their operators this way for that reason.

eSIM, iSIM and soft SIM, represent the next generation of SIM technologies. Each offer a distinct set of capabilities with some presenting more difficulties for IoT than others.

We offer a range of options suited to your specific IoT use case, whether that’s eSIM, iSIM or on-device connectivity software, and it is our firm belief that regulated technology that follows industry standards should be used. For that reason, we do not offer soft SIMs.

The connectivity landscape is constantly changing and you don’t need to invest in unregulated technologies to achieve ultra-high reliable, global IoT connectivity. In the past year, we’ve been working on a number of new innovations using industry-approved technologies, including the introduction of AnyNet SMARTconnect™ on-device IoT connectivity software solution, launching our first iUICC / iSIM with Sequans and Kigen at MWC in 2023, and architecting a new solution to support our customers with the GSMA’s nascent remote SIM provisioning standard, SGP.31/32.

Our IoT connectivity solutions are recognised by leading industry analysts at Gartner, Transforma Insights and Kaleido Intelligence. In November 2023, Kaleido Intelligence announced that Eseye is the #1 Champion for eSIM connectivity when compared with twenty-five other vendors, which further cements our technical expertise and capabilities in this highly competitive space.

Ian Marsden

Founder & CTO


Ian has a passion for developing technology-based solutions that deliver real improvements to businesses, the environment and quality of life.

Previously he co-founded CompXs to deliver the world’s first ZigBee design. Prior to CompXs, Ian held senior software leadership roles at Philips and has since spearheaded the ground-breaking innovation of our global AnyNet Secure cellular solution.

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