Yes, I think it is very much based on the type of business that you are trying to make most SaaS companies use arr as a measure but for a business like Twitter or Facebook, this would have been useless to start with so it is very much based on your business model.

In terms of tools I do not know for my own project I am using Google analytics to measure users it is pretty primitive but it is free. Hopefully, someone else can help you if there is a particular tool or metric you are looking to measure.

I hope this helps

All the best
Sponsored Worker

Thanks I found it