iPhone 101: What is an ESN and how can it go bad?

Getting your older iPhone ready to sell on eBay? You might notice listings that advertise good ESN and bad ones. Just what are those?

An ESN is the electronic serial number assigned to your iPhone and is used with CDMA phones instead of SIM cards. There are several good guides through eBay about what an ESN is and how it can go bad.

1. What does it mean if I have a bad ESN? A bad ESN means you can't activate an iPhone on your current carrier. For example, if you purchase an iPhone with a bad ESN from someone who used it on Verizon, then you won't be able to activate that phone on Verizon.

2. How do I get a bad ESN? You can get a bad ESN three ways: reporting your phone as lost or stolen, if the phone is still active on your wireless account or if you have an outstanding balance on your account.

3. How do I make sure I have a clean ESN? According to MaxBack, make sure your phone is completely off your wireless account before delivering it into the hands of a new owner. Settle any outstanding balances as well. You can see if your ESN is clean through a check on Swappa. It'll let you know if the ESN is activated on an account or not.

4. What do I do if I bought a phone with a bad ESN? An ESN can only be cleared by the original owner of the phone, so you would need to contact that person.