I am currently in process of planning a new web application for a client. Part of the project entails creating a progressive web application (PWA) for a specific segment of the client's users who are doing "fieldwork". While working in the field these users periodically report back to headquarters currently via a web  based interface. However the users often have little (lie-fi) to no internet connectivity at all (offline). That means that the can't report back using the web based interface when they are supposed to.

Enters the PWA! Using novel features available in modern smart phones, reporting can be possible even when the user is offline. In that case the report will be stored locally on the user's smart phone and will automatically get sent back to headquarters, once the smart phone obtains internet connectivity again.

However, before I can be sure that this is feasible solution, I need to be certain that the mobile devices that our users carry with them, actually have the technology available to support this bright idea. I currently only have anecdotal reports which is not enough to either validate or invalidate the idea. A much better approach is obviously using actually data to make an informed decision upon.

There are many ways to obtain this data, but a nice and easy method is using Google Analytics and their Event Measurement. Using a custom script (see below) I will check what browser features are available to the user (eg. does the browser support storing data locally while offline) and store that information using Event Measurement, along with all the other information that Google Analytics picks up on its own.

After a period of time (I my case I suspect a couple of weeks, but it depends on how active your users are) you will have collected enough hard data on what browser features your users have available. It will be much easier to make an intelligent decision on how to proceed.