Known for "Integrated Circuit Card Identifier". ICCID is a unique number assigned to a SIM card used in a mobile phone or any other cellular device. It provides a standard way of identifying each mobile device connected to the cellular network.
ICCID Format
89-CCC-II-AIN-checksum, where 89 is the MII (Major Industry Identifier) representing "Telecommunications administrations and Private operating agencies". CCC is the international Counntry Calling Code, II is the carrier's Issuer Identifier, and AIN is the Account Identification Number.
For example, 89-91-10-120000320451-4 is a SIM number in ICCID format. 89 is the MII required for all SIM numbers. 91 is the CCC representing India. 10 is the II representing Airtel as the carrier. 120000320451 is the AIN representing the SIM card owner's account. 4 is the checksum to ensure the integrity of the entire SIM number.
The format of the ICCID is: MMCC IINN NNNN NNNN NN C x
MM = Constant (ISO 7812 Major Industry Identifier)
CC = Country Code
II = Issuer Identifier
N{12} = Account ID ("SIM number")
C = Checksum calculated from the other 19 digits using the Luhn algorithm.
x = An extra 20th digit is returned by the 'AT!ICCID?' command, but it is not officially part of the ICCID.
ICCID vs IMEI
Both ICCID and IMEI (International Mobile Equipment Identity) are unique IDs for mobile devices. However, the IMEI is tied to the hardware while the ICCID is assigned to the removable SIM card. So a smartphone will always have the same IMEI, but if the SIM card is changed then the ICCID will change.
Cellular providers activate devices based on their ICCID rather than their IMEI. Since each mobile account is linked to an ICCID, it is possible to use the same device on multiple networks by simply swapping SIM cards.
