Good question! As Slack charges for active users, this is one that comes up. I did a quick search and found their helpful support peeps answered this:
And further defined:
So, after 14 days of cursor/click inactivity, a user is inactive and is no longer charged. Pretty solid to me.
Originally Posted: https://www.quora.com/Who-does-Slack-count-as-an-active-member
Originally Posted On: 2016-10-07