[meatball66]

I have looked at a ton of threads on the topic of ESN and IMEI, but have a question(s) that has not been definitively answered. I am hoping I can find the answer and move on with my life. ;-)

I am on at&t. I would like to buy a spare Z10 or Z30 from eBay, Craigslist, the guy down the street, it doesn't matter where I get it. I see many listed with bad ESNs. I know what the ESN and IMEI are, but I can not find whether a bad ESN phone will work on at&t without "unlocking" it. So, can someone explain the difference between ESN, IMEI, unlocked, how they work with carriers and which phones work on which carriers?

Thanks in advance for any responses or pointers to other threads that cover this that I may have missed.

[Sith_Apprentice]

I have looked at a ton of threads on the topic of ESN and IMEI, but have a question(s) that has not been definitively answered. I am hoping I can find the answer and move on with my life. ;-)

I am on at&t. I would like to buy a spare Z10 or Z30 from eBay, Craigslist, the guy down the street, it doesn't matter where I get it. I see many listed with bad ESNs. I know what the ESN and IMEI are, but I can not find whether a bad ESN phone will work on at&t without "unlocking" it. So, can someone explain the difference between ESN, IMEI, unlocked, how they work with carriers and which phones work on which carriers?

Thanks in advance for any responses or pointers to other threads that cover this that I may have missed.

AT&T does not use ESNs, this is mostly a CDMA thing. You need to check the IMEI. If you are buying a Sprint or Verizon device and want to use this on AT&T, you will need to have it unlocked, if it has not yet been. Some come factory unlocked.

ESN - Being phased out by CDMA providers in favor of the MEID
IMEI - GSM and LTE equipment identifier
Unlocked - Means the device is able to read SIMs from other carriers (other than the branding on the device)

To see which works on your carrier, you will need to know what model device (STL100-x or STA100-x) to find out which frequency bands are supported.

[DaFoxGrey]

See:
What is a bad ESN cell phone and should I buy it? | eBay

[meatball66]

Thanks for the info. That clears things up for me and maybe some others. I appreciate it.