Android includes some data tracking tools, many of which are buried deep in the settings. It plugs into the stats already collected by your phone, so it will provide insight into your data usage immediately after installation. Datally tracks data usage by app and time, allowing you to see what used data and when it happened. In addition to tracking your data usage, Datally can help control it. Apps can be completely blocked via the floating UI if you want to prevent any data usage.

Source: Forbes November 30, 2017 17:48 UTC