How do I create a KPI for active mobile users in Google Analytics?

A lot of users recognize the importance of tracking mobile active users in Google Analytics. The thing is, whether it’s mobile or Web, we first have to define what an active user is.
Here are some hints to define an active user in Google Analytics.
Returning visitor: We can filter out the new visits up front. An active user should be a returning visitor.
Visit count: How many visits should a user have made to be considered as active? Once a week? Twice a month? Using the Google Analytics visit count dimension, you can determine that.

Days since last visit: It’s an alternative of the one above. An active user can be a visitor who visited the website in the past X days.

Goals or events: An active user might be a visitor who completed a goal or triggered an event as well.

Page depth: The page depth illustrates the number of pages viewed during a visit. We could state that anything below 3 pages of an engaging section, like the shopping cart, isn’t really an active user.

Once you have defined what your active user is, you can filter the data using the device category to get only mobile active users. Here’s what a filter for active mobile users would look like:

ga:visitorType==Returning Visitor;ga:deviceCategory==mobile;ga:visitCount!=1;ga:totalEvents>=1

That’s it! You can now report on mobile active users with your Google Analytics data.