Mobile Technology & IMEI Checking Glossary

Activation Lock is a security feature developed by Apple that links an iPhone's hardware identifiers (IMEI and Serial Number) to the owner's Apple ID on Apple’s activation servers. Once engaged on App...

Albert is the codename for Apple's centralized activation servers, which handle device restriction policies and store Carrier Lock statuses. When an iPhone connects to the internet during initial setu...

Apple Business Manager is an enterprise platform that allows corporations and educational institutions to deploy Mobile Device Management (MDM) profiles to remotely wipe, lock, and control their hardw...

AppleCare+ is Apple's extended warranty tier that protects devices against manufacturing defects and accidental damage. Standard prepaid AppleCare+ plans are tied directly to the device's serial numbe...

The GSMA Blacklist is a centralized global database (Equipment Identity Register) where cellular carriers record the IMEI numbers of devices reported as lost, stolen, or involved in financial fraud. O...

A Carrier Lock (or SimLock) is a software restriction set by a cellular provider that ties an iPhone's baseband modem to a specific mobile network. The device will rigidly reject SIM cards or eSIM pro...

Dual SIM Dual Standby (DSDS) is a modern cellular modem architecture that allows a smartphone to handle multiple distinct network routes simultaneously, such as one physical SIM and one digital eSIM. ...

The EFS is a protected system partition (functioning similarly to NVRAM on other architectures) within an Android smartphone's internal storage dedicated solely to radio frequency calibration, baseban...

An EID is a unique 32-digit serial number physically embedded into the phone's secure eUICC chip, which acts as a digital vault for storing eSIM profiles. Unlike a 15-digit IMEI that identifies the mo...

An eSIM is a digital subscriber profile that is downloaded directly into a device's embedded secure chip, replacing the need for a physical plastic SIM card. On dual-SIM smartphones with a physical tr...

The eUICC is a secure integrated circuit chip physically soldered directly onto a smartphone's motherboard to hold digital eSIM profiles. This chip is permanently identified by its 32-digit EID number...

Find My is Apple's location tracking and anti-theft network that securely links a device's hardware identity (IMEI and serial number) to an owner's Apple ID. Enabling this feature automatically engage...

The GSMA is a global organization representing mobile operators that manages the centralized worldwide registry of device identifiers and Equipment Identity Registers. It is responsible for issuing Ty...

The Global Service Exchange (GSX) is Apple's internal, centralized database network used by authorized technicians to verify hardware integrity, warranty status, and legal ownership.

An ICCID is a 19 or 20-digit serial number that acts as the unique identifier for a physical subscriber identity module (SIM card). Unlike an IMEI, which is permanently tied to the phone's hardware, t...

The IMEI is a unique, 15-digit numerical code assigned to the baseband processor of every cellular device, acting as a permanent digital fingerprint for the hardware. Cellular carriers rely on this co...

IMEI 1 is the primary hardware identifier tied to a smartphone's first physical SIM slot, serving as the main network authentication channel. It is the master record for the entire device in the globa...

IMEI 2 is the secondary 15-digit hardware identifier found on modern Dual SIM Dual Standby (DSDS) smartphones, typically allocated to handle digital eSIM profiles or a second physical tray. It shares ...

The IMEISV (IMEI Software Version) is a tracking standard that replaces the traditional 15th mathematical check digit of an IMEI with a two-digit software version code. This appended code indicates th...

The IMSI  (International Mobile Subscriber Identity) is a unique number associated with a cellular network subscriber, stored securely on the SIM card, used to authenticate the user's billing account ...

IT Asset Disposition (ITAD) is a sector within the secondary electronics market focused on the secure data wiping, refurbishing, and recycling of consumer electronics on a massive commercial scale.

The Luhn algorithm is a mathematical checksum formula used to calculate the 15th check digit of an IMEI number to instantly detect accidental transposition or typing errors.

Mobile Device Management (MDM) is an enterprise protocol that allows corporations and schools to remotely wipe, lock, and manage their fleet of hardware devices.

The MEID (Mobile Equipment Identifier) is a 14-digit alphanumeric identifier in hexadecimal format (0-9, A-F) historically used to identify devices on older CDMA cellular networks, such as Verizon and...

The Mobile Switching Center (MSC) is a core routing hub within a carrier's network that handles real-time device authentication and call routing. When a device powers on, it transmits its identity dir...

NAND flash memory is the internal storage chip soldered to a smartphone's logic board that holds the operating system, device configurations, and user data.

NVRAM (Non-Volatile Random-Access Memory) is a highly encrypted, dedicated memory partition on a smartphone's logic board that securely stores the device identifier (IMEI), radio frequency calibration...

The Secure Enclave is an isolated, highly secure coprocessor within modern Apple devices that runs independently of the main CPU to store sensitive data like cryptographic keys.

The Serial Number (SNR) within an IMEI is a unique 6-digit sequence (positions 9 through 14) that identifies the exact, individual hardware unit within a specific model batch.

The Type Allocation Code (TAC) consists of the first eight digits of an IMEI number and is issued by the GSMA to officially identify a specific manufacturer brand and device model.

A UDID is a unique alphanumeric identifier assigned to Apple devices, which is combined with the IMEI and Serial Number to authenticate the hardware during activation.

USSD (Unstructured Supplementary Service Data) is a standard communications protocol used by cellular devices to query the device's firmware or communicate directly with carrier computers. The most cr...