What metrics are tested to measure user retention in SaaS product?

Main metrics:

Retention 1, 7, 30, 90 days

Churn 1, 7, 30, 90 days It can also be metrics and engagement:

Time on page - you can look at some important pages, for example, time in the news feed

Time on site / Average Session Duration - total time per day or average time per session

Bounce rate - % of visitors who left the site directly from the login page or viewed no more than one page of the site. This metric may not be relevant for everyone, for example, if the entrance starts from the news feed page, it makes no sense to watch it

What does user activation mean and what metrics are important there?

Number and % of users, who added name, last name, profile picture and other info - Number and % of new users who added first name, last name, profile picture and other info

Number and % of users, who browsed X posts— Number and % of new users who viewed at least X posts

Number and % of users, who liked X posts — Number and % of new users who gave at least X likes

Number and % of users, who spent X time in the service — Number and % of new users who spent X time in the service

It is important to choose the right event, which we will consider activation, to learn about the aha moment through analytics or in an interview, and the metric will be conversion to this action. Large social networks may not look at activation, because their new users hardly grow, only old ones wake up