How To Check If Custom Android Is Rooted?

We've bought some custom android tablets, that we're going to use as kiosk tablets. For our kiosk app to work properly the app needs root access. How can I check if the device is

Solution 1:

Had to try a number of different root tools. Turns out KingRoot (https://kingroot.net/) did the job. Afterwards Root Checker says that it is rooted correctly and my app works again.

Solution 2:

There is this nice guide which you can follow to check if the phone is rooted or not.

Link to website