Difference between IMEI, IMSI, ICCID and MSISDN numbers

The number of connected mobile devices is growing rapidly, and the new 5G networks will only accelerate it. We have more than 8 billion mobile subscriptions already in the world, and now with the growth of the Cellular Internet of Things (CIoT), we can expect an even larger number of connected cellular devices. As more devices join the network, device identification becomes increasingly important in a world where device manufacturers are continuously evolving identification methodologies. Accurate identification of mobile devices is vital for mobile network operators for assigning the right services to the right devices. Mobile networks use various unique codes to be able to dispatch the services relevant to specific subscribers accurately. IMEI, IMSI, ICCID and MSISDN are some of the key codes required for the identification of mobile devices.

IMEI is a 15 digit number assigned to every cellular device for each of its SIM slots; IMSI is a 15 digit number assigned to the SIM of a mobile subscriber; ICCID is a number that identifies the chip of each SIM card; MSISDN is the full mobile number including the country code and any prefixes.

What is it linked to?What does it look like?
IMEIPhone15 digits all numeric
IMSISIM15 digits all numeric
ICCIDSIM~20 digits all numeric
MSISDNSIMFull mobile number with country code and all prefixes
—IMEI vs IMSI vs ICCID vs MSISDN—

So basically, the IMEI number is linked to the mobile device (e.g. your smartphone), whereas IMSI, ICCID and MSISDN are linked to the subscriber or SIM (Subscriber Identity Module). These concepts work the same way if you are using a regular plastic SIM or an embedded SIM (eSIM).

IMEI vs IMSI vs ICCID vs MSISDN

IMEI stands for International Mobile Equipment Identity, and it is a 15 digit number that is linked to the mobile phone or any other cellular device. If you change the SIM in the phone, it has no impact on the IMEI number. IMSI stands for International Mobile Subscriber Identity and it is a 15 digit number that is linked to the SIM card and not the mobile phone. ICCID stands for Integrated Circuit Card Identifier and it is usually a 20 digit number that is assigned to the hardware chip of each SIM card. It is not linked to the mobile number so if you move your mobile number to another SIM, then the ICCID will change because the number will be linked to another SIM with a new ICCID. MSISDN stands for Mobile Station International Subscriber Directory Number and it is your full mobile number, including the country code (e.g. 44 for the UK) and any prefixes (e.g. 07 for the UK). For example, if your UK mobile phone number is 07000000000, then the MSISDN will be 447000000000 (only example).

Identifiers: IMEI for mobile phone and IMSI, TMSI, ICCID and MSISDN for the SIM
Identifiers: IMEI for mobile phone and IMSI, TMSI, ICCID and MSISDN for the SIM

What IMEI stands for and what it means

IMEI stands for International Mobile Equipment Identity, and it is a unique fifteen digit number assigned to every cellular device for each of its SIM slots. The IMEI number is unique to every cellular connection; therefore, if you have a dual-SIM phone, your phone will have two IMEI numbers.

Cellular devices like smartphones are SIM-enabled which means we need to insert a SIM card to connect them to the mobile network. We have multiple SIM options in newer mobile phones, including a physical compartment for slotting in a plastic SIM and an embedded SIM called eSIM inside the phone that you can manually assign to a mobile network. The IMEI number is unique to every cellular connection; therefore, if you have a dual-SIM phone (a phone that can take two SIMs), whether plastic or electronic, your phone will have two IMEI numbers. International Mobile Equipment Identity can be assigned to every mobile cellular device, including (but not limited to) mobile phones and mobile broadband data cards. It is programmed into the mobile device by the device manufacturer. The IMEI number stays with the mobile device over its lifetime and must not be modified. Only the manufacturers of the mobile device are allowed to assign this number. The act of changing this number is called “unblocking” which is a criminal offence under UK laws.

What does an IMEI number look like?

The IMEI number is a 15 digit code, all numeric, which shows up on all mobile phones in the same number format. However, the user interface (UI) design may differ depending on the device manufacturer and operating system. Below are some pictures to show you exactly what the IMEI number looks like on smartphones.

what is imei number
Example: IMEI number displayed on a Huawei Android phone (We have updated the screenshot to replace the actual IMEI)
Example of how IMEI is displayed on an iPhone (We have updated the screenshot to replace the actual IMEI)
Example of how IMEI is displayed on an iPhone (We have updated the screenshot to replace the actual IMEI)
Example: IMEI number displayed on an old Samsung Android phone (We have updated the screenshot to replace the actual IMEI)
Example: IMEI number displayed on an old Samsung Android phone (We have updated the screenshot to replace the actual IMEI)

What is the IMEI number used for?

The IMEI number is a unique device identifier that lets mobile operators know which device is trying to access the mobile network. Unlike IMSI (International Mobile Subscriber Identity), which is a SIM-specific identifier, IMEI is unique to the device itself. If a mobile phone gets lost or stolen, the IMEI number is the way to block the handset from being misused. As a mobile phone user, if you lose your phone for whatever reason, you need to ensure that you contact your mobile operator to block the IMEI and IMSI because IMEI is specific to your device, and IMSI is specific to your SIM. IMEI number allows an operator to place a specific mobile phone on a blacklist which means the phone is prohibited from accessing the mobile network no matter which SIM is inside it. The device registration and tracking capability reside within the mobile core network. Equipment Identity Register (EIR) is the entity within the mobile core network that stores the IMEI information in a database.

How can I check my IMEI number?

There are multiple ways of checking IMEI numbers. The quickest way to check your IMEI number is to type a sequence *#06# on the dial-pad of your cell phone, which will display the IMEI number on the phone screen. You can also check the IMEI number by going into the ‘Settings’ menu of your phone.

For iPhones, you need to go to “Settings”–> “General” –> “About” and then scroll down to find your IMEI number. For Android phones, generally, you can go to “Settings”–>”About phone” to find the IMEI number. You can also check the IMEI number on other devices like SIM-enabled tablets, smartwatches and cellular mobile broadband routers. Check out this dedicated post to learn some ways of checking the IMEI number on your cellular devices.

What is IMSI (International Mobile Subscriber Identity)?

IMSI or International Mobile Subscriber Identity is a unique 15 digit number assigned to each SIM card to identify a mobile subscriber within the network. The network uses a temporary IMSI (TMSI- Temporary Mobile Subscriber Identity) during most communication to ensure privacy of the mobile user.

IMSI is usually a 15 digit number where the first three digits represent the Mobile Country Code (e.g. 234 for the UK), and the next two digits represent the Mobile Network Code (e.g. 15 for Vodafone UK), and the last ten digits represent the Mobile Subscriber Identification Number.

The Mobile Subscriber Identification number is the identity of the subscriber within the Public Land Mobile Network (PLMN). IMSI is used whenever the mobile phone tries to access the mobile network irrespective of which technology it uses, i.e. 2G GSM, 3G UMTS, 4G LTE or 5G NR. As mentioned above, the mobile network may use a temporary IMSI called TMSI (Temporary Mobile Subscriber Identity) instead of IMSI to ensure the subscriber’s confidentiality. A user does not need to know or worry about their IMSI number; however, they can use available apps in app stores to find out their IMSI number. Mobile operators use IMSI as the identity of the mobile subscriber to assign and manage any services allocated to that particular subscriber. For example, the first two parts of the IMSI number, i.e. Mobile Country Code and Mobile Network Code, can indicate when a mobile user is outside of the country and roaming, allowing mobile operators to apply the correct billing.

—Example of IMSI and ICCID numbers—

What is the ICCID number and how to find it?

ICCID stands for Integrated Circuit Card Identifier and is a number that is assigned to the SIM hardware. A SIM card is essentially an integrated circuit board that is programmed by the mobile operator (MNO or MVNO). The golden part of the SIM is the chipset that the ICCID number is assigned to.

This number is usually printed on the back of the SIM card, but your phone can read this number, so if you need this number, you can easily find it without having to get your SIM out of the phone. The ICCID number is usually 19 or 20 digits long and is specific to each SIM card. It has nothing to do with your mobile phone number because it is just for the chip on your plastic SIM. If you damage your SIM card, you can move your mobile phone number to another plastic SIM or eSIM.

ICCID number is assigned to the chip of your SIM and can be found on the back of your SIM card

An easy way to find your ICCID number is to go to Phone Settings –> About phone and then the network or SIM information. On an iPhone, you can simply go to Settings–>General–>About to see the below screen, and you can just scroll down to the section where ICCID is displayed along with the IMEI number.

ICCID number on an iPhone (only an example)

The first two digits in an ICCID represent the industry code for “telecom”, which is 89. The next one to two digits are reserved for the international country code (e.g. 44 for the UK). The next one to four digits represent the code for the network that issues the SIM card, and the remaining digits are unique identifiers for your SIM. ICCID is the number that identifies your SIM card and is required by some mobile operators when setting up the online account for your subscription.

—How to read an ICCID number—

What is the MSISDN number and how to find it?

MSISDN stands for Mobile Station International Subscriber Directory Number, and it is just your complete mobile phone number with the country code and any prefixes that are part of your mobile number. It is used for identifying your mobile phone number for calls, text messages and mobile data.

If you need to know your exact MSISDN number, there is a very straightforward way to find out. For example, in the UK, a local mobile phone number has 11 digits, and all mobile phone numbers start with 07. So suppose your mobile phone number is 07000000000 and you need to find the MSISDN number for this particular phone number. As it is a UK number, we need to add the international country code, which makes it something like this: +44 (0)7000000000 or 0044 (0)7000000000. To get the MSISDN number, you need to write the complete mobile number, remove the 00 or + sign from the country code, and remove the ‘0’ from the 07. So if we apply this method to the mobile phone number in question, we will get something like this: +44 (0)7000000000 or 0044 (0)7000000000. The exact MSISDN number will, therefore, be 447000000000.

Conclusion

IMEI, IMSI, ICCID and MSISDN are unique codes used to identify a mobile phone user within the mobile network. IMEI stands for International Mobile Equipment Identity, and it is a unique number assigned to every mobile device, including mobile phones, dongles, cellular IoT sensors, data cards etc. IMSI stands for International Mobile Subscriber Identity, and it is a unique number assigned to each mobile subscription through the SIM card used by the mobile device. ICCID stands for Integrated Circuit Card Identifier, and it is a unique number assigned to the hardware (chipset) of each SIM. Finally, MSISDN stands for Mobile Station International Subscriber Directory Number, and it is the complete mobile phone number, including the country code and any prefixes.

Here are some helpful downloads

Thank you for reading this post. I hope it helped you in developing a better understanding of cellular networks. Sometimes, we need extra support, especially when preparing for a new job, studying a new topic, or buying a new phone. Whatever you are trying to do, here are some downloads that can help you:

Students & fresh graduates: If you are just starting, the complexity of the cellular industry can be a bit overwhelming. But don’t worry, I have created this FREE ebook so you can familiarise yourself with the basics like 3G, 4G etc. As a next step, check out the latest edition of the same ebook with more details on 4G & 5G networks with diagrams. You can then read Mobile Networks Made Easy, which explains the network nodes, e.g., BTS, MSC, GGSN etc.

Professionals: If you are an experienced professional but new to mobile communications, it may seem hard to compete with someone who has a decade of experience in the cellular industry. But not everyone who works in this industry is always up to date on the bigger picture and the challenges considering how quickly the industry evolves. The bigger picture comes from experience, which is why I’ve carefully put together a few slides to get you started in no time. So if you work in sales, marketing, product, project or any other area of business where you need a high-level view, Introduction to Mobile Communications can give you a quick start. Also, here are some templates to help you prepare your own slides on the product overview and product roadmap.

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