What is an Electronic Serial Number (ESN)?

Electronic Serial Number (ESN) is a CDMA phone identity number, rather than a mobile number. On GSM phone, it’s name is IMEI number. Electronic serial numbers (ESNs) were created by the U.S. Federal Communications Commission (FCC). The administrative role was taken over by the Telecommunications Industry Association in 1997 and is still maintained by them. ESNs are currently mainly used with CDMA phones.

The Electronic Serial Number (ESN) is an identification number for the handset of a mobile subscriber in non GSM technologies. The ESN forms together with the mobile telephone number (Mobile Identity Number: MIN) the identity of a mobile subscriber. In GSM this number is called IMEI.

Although ESN, MEID, and IMEI are distinct identification standards, ESN has come into popular usage as a catch all for the serial number (in whatever format it may be in) for the phone in question. As such, you’ll see references to the ESN number of an ATT-branded iPhone even though that phone actually as an IMEI, not an ESN. In fact, we’re going to use it in the same fashion for the rest of our response unless we’re explicitly referring to a specific identification number system.