SIM Cards, eSIM, iSIM, and Soft SIM: decoding every SIM format

For many, a SIM profile and SIM card mean the same thing. In reality, however, a physical SIM card is merely one of many formats that store the data that makes up a SIM profile.

When most people imagine a SIM, they picture a classic silicon and PVC SIM card. For decades, these cards have been the world's most popular SIM format, ubiquitous in personal mobiles and industrial connected devices. In recent years, though, this has undergone a fundamental change. Spurred by a number of factors, from environmental concerns about plastic waste to technological developments in smartphone hardware, physical SIM cards are being replaced by digital SIM formats, including iSIM, Soft SIM, and, increasingly, eSIM. By 2030, eSIMs are expected to be the SIM format found in most smartphones worldwide.

Here, we explore the reasons behind this shift, and detail every SIM type.

A brief history of SIM

SIM cards have been in constant use since their commercial launch in 1991. Back then, “card” was an apt description – the first physical SIMs were the same size and material as credit cards.

In the years since, SIM cards have gotten smaller and smaller, from the Mini-SIM or Standard-SIM launched in 1996 to 2003’s Micro-SIM and the 2012 Nano-SIM, which is just over a centimeter in length. However, the same dense grouping of materials and plastic surroundings remains. When first produced, Nano-SIMs are still usually housed in a plastic surround and need to be “popped out” before use. While they may now occupy less space within a device, their production, packaging, and distribution still means SIM cards have a significant environmental impact.

While the classic SIM card format may be iconic, this form factor has become a drawback over time. As device manufacturers race to pack the most attractive features into each new smartphone release, the required SIM tray and SIM card is becoming increasingly burdensome, occupying precious space within the phone's interior.

Thinner, lighter housing and a market expectation for increasingly faster processors, more powerful cameras, and longer battery life have driven the push towards new SIM formats with a smaller internal footprint. The marketing for the upcoming iPhone 17, for example, or the recent Apple Watch 10, both focus on their slimline designs. The manufacturer-led shift towards eSIM was further illustrated by Apple’s eSIM-only 2022 iPhone 14 model, which helped to familiarize the concept of software SIMs among the general public.

The SIM card is far from obsolete though: in specific cases, it's still the most effective connectivity option. This mainly applies to particular niches within the Internet of Things (IoT) and machine-to-machine (M2M) sector. In these instances, the simplicity of SIM cards and their compatibility with older devices can make them cheaper to implement than eSIMs, and allow them to be retrofitted to older IoT devices that aren’t eSIM compatible.

“Ruggedized SIMs” are another example, being SIM cards specifically built to endure extreme conditions and years of constant usage. But as eSIMs continue to take hold in the telco space, this is expected to change.

For consumers, manufacturers, and operators, nearly every issue associated with SIM cards is solved by eSIM. This new era of eSIMs is made possible by Remote SIM Provisioning (RSP), a GSMA specification that determines how SIM profiles are distributed to individual devices over-the-air (OTA), rather than manually inserted via a SIM card.

The rise of eSIM

Of all the successors to SIM cards, eSIMs are by far the most used, most useful, and most likely to shape the future of telecoms.

Short for “embedded SIM”, an eSIM is a software-based SIM profile that is transmitted to and saved on a microchip (known as an eUICC), which is physically integrated within the hardware of the receiving device. These eUICC-enabled devices can save and store multiple eSIM profiles simultaneously, and users can instantly and remotely activate, recall, and switch between different eSIMs within seconds.

eSIMs are already on track to overtake SIM cards as the most-popular SIM format worldwide, and are projected to account for 98% of US smartphone connections by 2028. Their wide range of applications has made them the overwhelming favourite in the IoT sector.

In fact, eSIMs were initially developed for IoT usage back in 2012. Their versatility and cost-efficiency soon saw them make the transition to consumer devices, where they are now a standard feature of new smartphone releases.

Introducing iSIMs

An iSIM (Integrated SIM) is similar in concept to an eSIM, though stored on an even smaller area. Like an eSIM, an iSIM consists of a software-based SIM profile that is transmitted and stored on a hardware component within the body of the receiving device. The primary difference between eSIM and iSIM is their storage location. While an eSIM is saved to a discrete eUICC chip, an iSIM can be stored on a dedicated space within the device’s main processing chip, negating the need for an external eUICC component. This space is far smaller than an eUICC, further minimizing the SIM’s footprint. This minimal impact iSIM amplifies the advantages of eSIMs, further simplifying the supply chain and manufacturing processes for new connected devices, and freeing up more internal real estate (iSIMs occupy up to 98% less space than eSIMs). This makes them particularly attractive in the rapidly growing wearable tech market, where every spare millimeter of space is a premium.

iSIMs also address a growing concern within the IoT and telecommunications industry: power consumption.

The average power consumption of an iSIM is estimated to be around 70% less than a physical SIM card. While this is a useful cost-saver, it's also an essential requirement for building a more sustainable IoT industry. The projected power consumption of connected devices in coming years is enormous, as worldwide data demands experience an ongoing surge. For manufacturers and mobile operators, developing a scalable and environmentally-responsible connectivity infrastructure requires a series of strategic and technological shifts. Implementing eSIM or iSIM connectivity and Remote SIM Provisioning (RSP) is one method to curb power consumption and minimize logistical and manufacturing emissions.

iSIMs in IoT

Currently, iSIMs remain a niche market, despite GSMA standardization.

Their relatively new status means there is a lack of iSIM infrastructure in place, which can make them tricky to implement, particularly in multinational companies. Device manufacturers often need to negotiate new individual contracts and agreements with network operators in every country and region they wish to supply iSIM-enabled devices. This hurdle, coupled with a lower public awareness of iSIM and lingering security concerns, has slowed their adoption.

Nevertheless, iSIMs are a growing field, with the number of iSIMs projected to see an over-tenfold increase between 2024 and 2026

By 2028, over 200 million iSIM-connected devices are expected to be in operation.

Soft SIMs?

Soft SIMs, also known as virtual SIMs or cloud SIMs, are the concept of a software-based SIM profile taken to its logical conclusion: these are digital-only SIMs, with no physical components required at any point in their lifecycle. All data required for the SIM to function is stored in the device’s memory, rather than a dedicated hardware chip.

In its 2015 report on SIM evolution, the mobile industry’s leading regulatory body the GSMA strictly distinguishes between Soft SIMs and software-based SIM formats like eSIM and iSIM: “(in embedded SIMs) ...the physical hardware element is always present and adds an indispensable layer of security. A ‘Soft SIM’ would be a solution with no SIM hardware and where all SIM functionality is carried out by a software layer.”

This description neatly illustrates the gap between soft SIMs and previous SIM formats, as well as revealing why Soft SIMs are still an unfinished product. While the potential advantages of a truly virtual SIM are clear for device manufacturers, mobile operators, and consumers, serious safety concerns remain.

In the decade since the GSMA report, demand for a viable Soft SIM has remained. Strides have been made towards delivering a workable solution. A software-only SIM is more at risk of cyberattack than a physical or embedded SIM, which are protected by a series of hardware and software measures. As it stands, soft SIMs remain unregulated by the GSMA, with no standardized security protocols in place, nor a fixed definition. This makes them a risky choice for manufacturers, though the potential advantages (including a vastly simplified supply chain and manufacturing process) mean that the demand for a truly virtual, secure, and reliable SIM format remains.

1GLOBAL Remote SIM Provisioning

While eSIMs have enjoyed widespread adoption across both the consumer and industrial connected device markets, it’s important to consider that they are still an emerging technology whose potential is still being explored. Mobile operators seeking to leverage the benefits of eSIM technology require an experienced partner with a viable RSP solution and flexible eSIM services.

1GLOBAL is an industry-leading eSIM service provider, having deployed more than 50 million eSIM profiles together with clients across dozens of industries, including IoT, consumer electronics, fintech, and telecommunications.

1GLOBAL's status as both an RSP supplier and telco ensures it provides the scalable solutions required for any growing business, with an unmatched level of customer support and personalized consultation. Learn more about 1GLOBAL Remote SIM Provisioning or speak to our team directly to find out how your business can implement RSP solutions.