IMEI no or International Mobile Equipment Identity No. is the soul of any mobile phone. Without a IMEI no a phone is useless, it will be device only for multimedia purpose. You can’t make phone call, SMS even internet. In android phone you will see that no signal is showing mean your android device has no proper IMEI. But why we are worried about IMEI as its embedded with phone and how can it be lost. Normally IMEI is embedded with firmware of your Android phone and there is nothing to be worry that it will be damaged or lost. But if you are advance user mean you have rooted your android phone and you want to install custom ROM on your android phone then you must take precaution. What is this precaution?
Precaution is you must make a IMEI backup of your Android phone. Now you will ask me why we need to make a IMEI backup if its embedded with system. Basically when you install Custom ROM then there is a slight risk that IMEI of your Android phone get corrupted or something like that. There is less probability of IMEI damage during custom ROM installation on Snapdragon chipset but if you are using MediaTek device then you are pushing your device on the verge of softbrick.
So better is make a IMEI backup before you install any custom ROM on your Android phone.
How To Backup & Restore IMEI in Android Phone
To make a IMEI backup your Android device must be rooted. So make sure your android device has root access by using this Root Checker tool.