IMEI vs MEID vs ESN: complete guide to mobile device identifiers

Key takeaway: IMEI (15 decimal digits) is used by GSM/LTE/5G networks, MEID (14 hex digits) by CDMA networks, and ESN (8 hex digits) is an obsolete CDMA format. With the convergence to LTE/5G, IMEI has become the universal standard. Convert between formats using our IMEI/MEID converter.

Mobile devices use different hardware identifiers depending on the network technology they are designed for. IMEI, MEID, and ESN are the three main identification systems that have coexisted across generations of mobile networks. Understanding their differences is essential for telecom professionals, fleet managers, and developers working with device data.

IMEI: the GSM/UMTS/LTE/NR identifier

Definition and scope

The IMEI (International Mobile Equipment Identity) is the unique identifier for devices on 3GPP family networks: GSM (2G), UMTS (3G), LTE (4G), and NR (5G). It is by far the most widespread system in the world, used by more than 90% of active mobile devices.

Structure (15 digits)

TAC (8 digits) + SNR (6 digits) + CD (1 digit)
│                 │                 │
│                 │                 └─ Check Digit (Luhn)
│                 └─ Individual serial number
└─ Type Allocation Code (manufacturer + model)

• TAC: identifies the manufacturer and model — see our TAC guide
• SNR: identifies the individual device among all devices of the same model
• Check Digit: calculated using the Luhn algorithm to detect input errors

IMEISV (16 digits)

The IMEISV (IMEI Software Version) adds a 16th digit indicating the device’s software version, replacing the check digit with a 2-digit SVN (Software Version Number). It is used internally by networks but rarely displayed to users.

For an in-depth presentation, see our complete IMEI guide.

MEID: the CDMA identifier

Definition and scope

The MEID (Mobile Equipment Identifier) is the unique identifier for devices on CDMA2000 networks (cdmaOne, CDMA 1xRTT, EV-DO). It was introduced in 2005 by the TIA (Telecommunications Industry Association) to replace the ESN whose address space was exhausted.

Structure (14 hexadecimal characters / 56 bits)

RR (2 hex) + XXXXXX (6 hex) + ZZZZZZ (6 hex)
│              │                │
│              │                └─ Manufacturer serial number
│              └─ Manufacturer code
└─ Regional Code (A0-FF reserved for legacy ESN)

The MEID is expressed in hexadecimal (14 characters) but can also be represented in decimal for easier user input.

MEID to pseudo-ESN conversion

To ensure backward compatibility with legacy network equipment that only supports ESN, each MEID can be converted to a pseudo-ESN (pESN) via a SHA-1 hash algorithm. The pESN is always in the range 0x80000000 - 0xFFFFFFFF.

MEID to IMEI conversion

Since CDMA networks converged toward LTE, some dual-mode devices carry both a MEID and an IMEI. The hexadecimal MEID can be converted to a 15-digit decimal format (sometimes called a “pseudo-IMEI”) to integrate into 3GPP systems, but this is not a genuine GSMA-assigned IMEI. To perform these conversions easily, try our IMEI/MEID/ESN Converter.

ESN: the legacy CDMA identifier

Definition and scope

The ESN (Electronic Serial Number) is the first mobile device identification system, created in the 1980s for AMPS (1G analog) networks and later adopted by CDMA networks (IS-95, cdmaOne).

Structure (32 bits / 8 hexadecimal characters)

MFR (8 bits) + SNR (24 bits)
│               │
│               └─ Serial number (16 million max per manufacturer)
└─ Manufacturer code (256 manufacturers max)

Why ESN was replaced

The ESN allows only 256 manufacturers and 16 million devices per manufacturer, for a theoretical maximum of approximately 4 billion identifiers. In practice, this space was exhausted well before that limit due to block allocation. The ESN was officially replaced by the MEID in 2005.

ESN and current devices

In 2026, the ESN is no longer used on any active network. The last CDMA networks (Sprint in the US, some operators in Asia) have been shut down. However, the ESN remains present in historical databases and some legacy systems.

IMEI vs MEID vs ESN comparison table

Feature	IMEI	MEID	ESN
Networks	GSM/UMTS/LTE/NR	CDMA2000	AMPS/CDMA
Length	15 digits (decimal)	14 characters (hex)	8 characters (hex)
Bits	~50 useful bits	56 bits	32 bits
Organization	GSMA	TIA	FCC (historical)
Capacity	> 10^14	~7 x 10^16	~4 x 10^9
Check digit	Yes (Luhn)	No	No
Status 2026	Active (global standard)	Residual	Obsolete
Global blacklist	GSMA IMEI Database	No global database	N/A

Relationships and conversions between identifiers

From MEID to IMEI

A MEID cannot be directly converted to a valid IMEI because the two systems have different allocation bodies (TIA vs GSMA). However, the decimal representation of a MEID has the same format as an IMEI, which sometimes creates confusion.

Modern devices that support both CDMA and LTE (like legacy Verizon models) have a MEID for the CDMA network and a separate IMEI for the LTE network, independently assigned.

From ESN to MEID

ESN to MEID conversion is not direct. A device with an ESN remains identified by its ESN; it does not receive a MEID. Only devices manufactured after 2005 received a native MEID.

Pseudo-ESN (pESN)

The pESN is derived from the MEID via SHA-1 hashing to ensure compatibility with network equipment that only supports ESN. The pESN is not unique (theoretical collision risk) but this does not pose a practical problem since collisions are statistically insignificant.

Impact on device verification

IMEI verification

IMEI verification is standardized and universal. Our TAC Lookup tool instantly identifies the manufacturer and model from the first 8 digits (TAC). The IMEI API offers programmatic verification with 100 free requests per month.

MEID verification

There is no public MEID database equivalent to the GSMA IMEI Database. MEID verifications are generally performed through the relevant CDMA carrier or via specialized third-party services.

ESN verification

ESN verification no longer has operational relevance in 2026, as all CDMA networks are shut down or being decommissioned.

Which identifier to verify in 2026?

In practice, the IMEI is the only relevant identifier in 2026 for the vast majority of use cases:

• Second-hand purchase: always verify the IMEI via TAC Lookup
• Fleet management: use the IMEI API to automatically identify devices
• Compliance: IMEI is the only identifier recognized by regulators for 4G/5G networks
• IoT/M2M: modern connected modules exclusively use IMEI

To deepen your knowledge of the mobile identifier ecosystem, check our technical glossary and our protocol decoder.