Every GSM enabled device will have its own International Mobile Equipment Identity number, more commonly known as an IMEI. This number is a 15 character reference that is used to identify devices on their networks. Each device has its own unique IMEI.
It is always a good idea to record this IMEI number for any device so that you can have it blacklisted should it get stolen or become lost.
How do you find the IMEI for your device? There are a number of different methods to do this.
Method 1
Using the number pad, enter *#06# as if you were making a phone call. Your device will display the IMEI number on screen.
Method 2
On an iPhone the IMEI can be identified by looking under:
Settings > General > About
Method 3
Look on the back of your iPhone. The original iPhone and iPhone 5, 5C and 5S have the IMEI engraved on the back as the last part of the 'Designed by Apple' text.
On an iPhone 3G, 3GS, 4 or 4GS the IMEI can be found on the SIM card tray.
Do not rely on this method if you are able to use method 1 or 2, as the rear casing may have been changed during refurbishment and a SIM card tray may have been replaced at some stage. However it can be useful to confirm the result of method 1 or 2.
Method 4
On an Android device you can find the IMEI by looking under:
Settings > About Phone > Status
Method 5
If your device has a removable battery. Power down the device and remove the back of the device, then take out the battery. The IMEI is usually printed on a sticker in the battery compartment.
Do not rely on this method if you are able to use method 1, as a sticker can be easily replaced. However it can be useful to confirm the result of method 1.
Method 6
If you still have the original packaging for your GSM device the IMEI will usually be on a barcode sticker stuck to the box.