Micro SIM card explained: Size, function & application
Last update: 03.10.2025
Important findings
- The Micro SIM is known as form factor 3FF and measures 15 × 12 mm.
- It differs from other SIMs only in terms of physical size; the chip and function remain the same.
- The Micro SIM card was introduced in 2010 as the third standardized SIM format for smaller mobile devices, an intermediate step between the Mini SIM and Nano SIM.
- Although rarely found in current smartphones, the Micro SIM card is still relevant in older devices and specialized applications (routers, GPS trackers, IoT).
- Advantages include compact design, reliability, and widespread use. Disadvantages include declining compatibility, limited availability, and lack of future-proofing.
Micro SIM (3FF): Compact format with continued relevance
The Micro SIM card (3FF) is a compact type of SIM format used in mobile devices. It was developed as the successor to the larger Mini SIM and represents a technical intermediate format. Although modern smartphones typically use Nano SIM or eSIM, the Micro SIM format remains relevant. In this article, we explain what a Micro SIM card is, how it works, and why it remains a vital component.
What is a Micro SIM card?
The Micro SIM is technically known as the 3FF format type. “3FF” stands for “third form factor” and refers to its position as the third standardized SIM card format. The card was introduced in 2010 to meet the requirements of increasingly compact mobile devices.
With a card size of 15 × 12 millimeters, the Micro SIM card is significantly smaller than previous formats. The primary function of the 3FF or Micro SIM card is to store user data such as phone number and network authorizations, and to enable access to the mobile network. It differs from the original SIM sizes solely in its physical shape. The chip and the data stored on it remain unchanged.
Micro SIM and the development of the SIM card formats
SIM card sizes and formats have evolved since their introduction in the early 1990s. The technology itself has not changed, but the format has been progressively reduced in size. The Micro SIM (3FF) represents an intermediate step in this development.
| Format | Designation | Größe (mm) | Introduction | Typical Use | |
|---|---|---|---|---|---|
| Full-size SIM (Standard SIM) | 1FF | 85,6 x 53,98 | approx. 1991 | Early mobile phones, test devices | |
| Mini SIM | 2FF | 25 x 15 | approx. 1996 | Mobile phones until around 2010 | |
| Micro SIM | 3FF | 15 x 12 | approx. 2010 | Smartphones, tablets | |
| Nano SIM | 4FF | 12,3 x 8,8 | approx. 2012 | Current smartphones | |
| eSIM | MFF2 | Permanently embedded | approx. 2016 | Smartphones, wearables, IoT devices | |
Format
- : Full-size SIM (Standard SIM)
- : Mini SIM
- : Micro SIM
- : Nano SIM
- : eSIM
Designation
- Full-size SIM (Standard SIM): 1FF
- Mini SIM: 2FF
- Micro SIM: 3FF
- Nano SIM: 4FF
- eSIM: MFF2
Größe (mm)
- Full-size SIM (Standard SIM): 85,6 x 53,98
- Mini SIM: 25 x 15
- Micro SIM: 15 x 12
- Nano SIM: 12,3 x 8,8
- eSIM: Permanently embedded
Introduction
- Full-size SIM (Standard SIM): approx. 1991
- Mini SIM: approx. 1996
- Micro SIM: approx. 2010
- Nano SIM: approx. 2012
- eSIM: approx. 2016
Typical Use
- Full-size SIM (Standard SIM): Early mobile phones, test devices
- Mini SIM: Mobile phones until around 2010
- Micro SIM: Smartphones, tablets
- Nano SIM: Current smartphones
- eSIM: Smartphones, wearables, IoT devices
Technical basics and function of the Micro SIM
The 3FF Micro SIM card is equipped with an integrated chip that stores essential information for using the mobile network. This includes the IMSI (International Mobile Subscriber Identity) for user identification, network information, access credentials, and, if needed, contacts and text messages. This data enables the unique identification of the user within the network.
After being inserted into a compatible device, the 3FF SIM automatically establishes a connection to the mobile network. Through standardized interfaces, it transmits the stored information, which is then verified and approved by the network. This allows access to voice services, mobile data, and other functions. With the help of an adapter, the card can also be used in devices with a different card slot format if required.
Application areas of the Micro SIM card size
After its introduction in 2010, the Micro SIM (3FF) was primarily used in smartphones and tablets. Due to its compact size, it offered a significant advantage over earlier formats: it saved space within the device without compromising technical performance. The Micro SIM card could be easily installed and quickly became the standard in many mobile devices of that time.
With the increasing spread of mobile applications, the Micro SIM found further areas of application:
- Mobile Wi-Fi routers and GPS trackers
- M2M devices and IoT applications
- Vehicle technology, logistics systems, and alarm systems
Today, the Micro SIM card is less commonly used in modern devices but remains relevant in long-lasting or specialized applications. It continues to perform reliably, especially in areas where proven technology and devices with fixed card slots are still in use.
Strengths and weaknesses of the Micro SIM (3FF)
For over a decade, the Micro SIM was a widely used format in mobile communication. It offered a compact design without requiring any technical compromises. In many devices, the 3FF SIM was the preferred choice before being increasingly replaced by smaller and more modern solutions.
| Advantages | Disadvantages | |
|---|---|---|
| Compact format | No longer compatible with current devices | |
| Technically reliable | Not a long-term solution due to new formats | |
| Easy to install | Adapter often required | |
| Long widespread use | Replacement only has limited availability | |
| Good network compatibility | Limited relevance for new technologies | |
Advantages
- : Compact format
- : Technically reliable
- : Easy to install
- : Long widespread use
- : Good network compatibility
Disadvantages
- Compact format: No longer compatible with current devices
- Technically reliable: Not a long-term solution due to new formats
- Easy to install: Adapter often required
- Long widespread use: Replacement only has limited availability
- Good network compatibility: Limited relevance for new technologies
The advantages of the Micro SIM card were primarily its compact size and long service life. It was flexible in use and reliably met all technical requirements. Nevertheless, it is now evident that the 3FF SIM card no longer meets current demands, as new devices rarely support the format and long-term compatibility is lacking.
Should you cut your Micro SIM yourself or request a replacement?
A larger SIM card can be carefully cut down to a Micro SIM card. This requires a suitable template, which is placed on the card and marked with a pen. The card is then trimmed along the markings using fine scissors.
Cutting the Micro SIM also carries risks: If the chip is damaged, the SIM may become unusable. In such cases, switching to a properly manufactured 3FF SIM is the better option. Mobile network providers and IoT providers usually offer the appropriate card formats free of charge.
3FF Micro SIM card between the past and the future
The Micro SIM was a significant step in the development of compact SIM formats. It combines small size with proven technology and has been used in a wide variety of devices for many years. Modern mobile devices increasingly rely on Nano SIMs or eSIMs, making the earlier Micro SIM format less relevant.
Nevertheless, Micro or 3FF SIM cards will continue to be used in certain areas, such as older cell phones, industrial control systems, and GPS trackers, as they function reliably in these applications and meet the requirements. However, their importance is likely to decline further in the future. Availability is decreasing, and in the long term, the market is clearly moving toward new standards.
FAQ about Micro SIM (3FF)
What is a Micro SIM card?
The Micro SIM card size measures 15 × 12 millimeters. It is technically referred to as a 3FF SIM. The integrated chip is identical to that of other SIM formats.
What is the Micro SIM used for?
The 3FF Micro SIM card is primarily used in older smartphones, tablets, mobile routers, and industrial devices. In these applications, it enables access to the mobile network. Today, it is mainly used in specialized applications.
Can a Micro SIM be cut to a Nano SIM?
Yes, it is possible to cut a Micro SIM format down to the Nano format using a template and with care. However, there is a risk of damaging the chip, so replacing the card through the provider is a safer option.
How long will the Micro SIM card still be supported?
There is no specific end date, but its use is rapidly declining. New devices rarely support this format, but the 3FF SIM remains usable in older devices for the time being.