Even if you’re leery about rooting your Android phone and installing a custom ROM, you can still try out some features and settings that aren’t turned on by default. Every Android phone comes equipped with the ability to enable Developer options, which lets you test some features and access parts of the phone that are usually locked away. As you might expect, Developer options are cleverly hidden away by default, but it’s easy to enable if you know where to look.
Find your Android Build number
Before you can enable Developer options on your Android phone or tablet, you’ll first need to find your phone’s build number. On most phones, you can simply type build number into the search field, but here’s how to find it on a few popular devices:
from Greenbot How-To