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What is ESN (Electronic Serial Number)

Electronic serial numbers (ESNs) are unique identifiers assigned to mobile devices, particularly older CDMA phones (AMPS, TDMA) in the United States. ESNs were created by the U.S. Federal Communications Commission (FCC) in the early 1980s to identify mobile devices on AMPS networks.

What is ESN

Understanding ESNs

ESNs were originally 32 bits long, with the first 8 bits representing the manufacturer code and the remaining 24 bits assigned by the manufacturer to each device. Later, the manufacturer code was extended to 14 bits, allowing for more manufacturers to be identified. ESNs can be represented in either 11-digit decimal or 8-digit hexadecimal formats.

Formats and Representation

  • Decimal Format: The first three digits represent the decimal value of the 8-bit manufacturer code (00 to 255), followed by eight digits derived from the remaining 24 bits (0000000 to 16777215).
  • Hexadecimal Format: Eight hexadecimal digits representing the entire 32-bit ESN.

Transition to MEIDs

As ESN codes started running out, a new serial number format called MEID (Mobile Equipment Identifier) was introduced by 3GPP2 in 2006. MEIDs are 56 bits long, allowing for a larger range of unique identifiers. While similar to the IMEI (International Mobile Equipment Identity) used by GSM phones, MEIDs can contain hexadecimal digits, whereas IMEIs are restricted to decimal digits.

Importance of ESN (Electronic serial numbers)

ESNs and their successor, MEIDs, play a crucial role in identifying mobile devices on cellular networks. Swappa, a popular platform for buying and selling used devices, places significant emphasis on verifying the ESN/IMEI during the listing review process. Providing accurate ESN information is essential for ensuring a smooth transaction and maintaining the integrity of the marketplace.

In summary, ESN (Electronic serial numbers) are unique identifiers assigned to older CDMA mobile devices, primarily in the United States. While ESNs have been largely replaced by MEIDs, understanding their format and significance remains important, particularly in the secondary device market. What is ESN (Electronic serial numbers) is a crucial piece of information for identifying and verifying the authenticity of mobile devices.

Lila Bennett

Lila Bennett

Lila Bennett, with 10+ years in eSIM tech, specializes in mobile connectivity solutions. She offers end-to-end eSIM services, from setup to support, for both businesses and consumers. Need eSIM integration or advice? Contact Lila anytime for expert assistance.