Finding the ESN / IMEI / MEID tied to your device depends a lot on the device itself.

In many cases, you can find the device identifier in any of the following ways:

  • On a sticker behind the device's battery
  • Via software on the "About" screen
  • On the device's box

Please note that in some instances, such as a for a replaced device, the ESN on the box may not match the ESN of the device. Swappa always asks for the ESN tied to the device.

Here is an old, but still useful page of how to find an ESN in Android: http://support.verizonwireless.com/clc/devices/knowledge_base.html?id=26468

This page shows how to find the serial number (ESN) for Apple products: http://support.apple.com/kb/HT1349