Each electronic device, including Android, has a unique identifier called serial number. The concept of the serial number is pretty similar to fingerprint on the humans in which none of the devices have the same serial number. Generally, the serial number is used by the manufacturers to track their device inventory for things like repair and warranty claims.
As a user, you need the serial number to claim the warranty or to get after-sale service for free. Typically, the serial number of an Android device and other electronic devices is printed on a sticker on the packaging box. What if you lose the box?
On the old Android device models, you can also find the serial number on the battery holder (you need to remove the battery to find it).
But, since today’s Android devices mostly have battery embedded on their body, you won’t be able to use this method anymore.
To find the serial number of your Android device if you lose its box, you can open the Settings menu of Android and select About Phone (or About Device on some older Android versions). On the About Phone screen, tap the Status option. There are several pieces of information displayed here, including the serial number of your Android device.
Once you found the serial number of your Android device, you should not share it anywhere, including social media. Remember, the serial number is a unique identifier of your device and there is no reason to make it public.