Formula
Count of distinct users with a qualifying event in the trailing 7 days
How to measure
Count distinct user IDs with at least one qualifying event within a rolling or calendar week.
Why track it
WAU better fits products used on a weekly, not daily, rhythm, avoiding the false alarm of low weekday-only DAU.
Example
A B2B analytics tool reports 40,000 WAU even though weekend DAU drops to near zero.