Having root privileges is the equivalent of administrator privileges on a desktop PC. It just enables you to fully access and change things on your Android phone. However, some find the extra functionalities dangerous or want it disabled due to certain functions and apps not working. Niantic, the creators of the vastly popular Pokemon GO app disabled the use of rooted Android phones and jailbroken iOS devices. There are ways to bypass this on Pokemon GO - see our deciated article for a guide on how to hide root.
You might also want remove root in order to receive official software updates, where some phone manufacturers prevent OTA updates if you're rooted - understandably you might want to permanently unroot your Android phone or tablet, so here's our guide. To check if you've got root, we recommend downloading Root Checker for free on the Play Store. Also see: How to root Android.
How to unroot Android: SuperSU unrooting
The SuperSU app is a must-have if you've rooted. Often you'll find the app installed after you've rooted, so look for it in your app drawer. If it's not installed you can download it for free on the Play Store.
When you've launched the app and ironically granted it root access, you'll see a few tabs, more specifically Settings. If you scroll down within the Settings tab, you'll see a Full unroot option. Tap it and you'll be prompted to completely unroot your device - when you continue, SuperSU will close. Reboot your device and you should now be unrooted.
Make sure to delete the app (among other root apps) after you've finished. Check with the Root Checker app to confirm a successful unroot. Also see: How to play Pokémon GO on rooted phone.
How to unroot Android: Universal Unroot app
Another app that allows you to fully unroot your Android device is, Universal Unroot. The app is paid-for, where it costs £0.78 on the Play Store. The app works in the same way as SuperSU, but where some have had problems with SuperSU, Universal Unroot has had the ability to fully unroot an Android device.
Once you launch the app, it will be self explanatory as you'll have the option to unroot your device.
It should be noted that some phone manfacturers make it hard for apps to work, such as Samsung (with KNOX) and LG (with LG eFuse) that make it very hard to unroot. If you have a device with these features, we would suggest navigating to XDA Developers' forums and asking (search before asking!) about your specific device. Check the Root Checker app to confirm a successful unroot.
How to unroot Android: ES File Explorer (manual unroot)
ES File Explorer is a free file manager app on the Play Store that allows you to use root functionalities to delete system apps.
This method involves a more manual apparoach and might to guarantee you a full unroot, as it's only used to delete system apps (including root-apps), but this won't necessarily remove root from your file system.
Nevertheless, it's worth trying if the prior two solutions haven't worked.
Open ES File Explorer and scroll down to Tools and turn on Root Explorer. You'll be prompted to enable root, accept and go back to the main menu by tapping '/'.
From your main directory, go into 'system' > 'bin' and find the 'busybox' and 'su' folders. Sometimes these folders might not exists on a device, but if they do, delete them.
Go back using '/' and open the 'app' folder. Delete 'superuser.apk' and then reboot your Android device. You should now be unrooted, but if you're not read on. Also check the Root Checker app to confirm a successful unroot.
How to unroot Android: Flash stock firmware
If you still have root, the best option would be to flash stock firmware. There are many guides per device on the XDA Developers forums - as each device is specific. You can also find many YouTube guides, such as this one from TotallydubbedHD that guide you on how to unroot and flash a stock ROM.
Remember, every device is different, so be sure to download the right stock ROM (including region) and follow written guides for your specific device. If you're unsure, be sure to ask before flashing, or else you might end up with a very expensive brick!
It should also be noted that you can sometimes unroot by simply installing an OTA update. Unfortunately, this isn't always the case with all phone manufacturers, where some won't allow you to update while rooted and others simply don't push out many OTA updates. You can always check the Root Checker app to confirm if you've successfully unrooted.