Active User (DAU, WAU, MAU)

An active user count is the number of users who did something that counts as activity within a window, usually a day, a week or a month. The important thing about the number is that it is a definition rather than a fact, and three separate choices sit inside it. What counts as active: opening the app, or performing the action the product exists for. What counts as a user: a login, a seat, a billing account, or a workspace, which matters enormously for business software where one account holds forty people. And the window, which is not neutral, because a monthly window flatters a product used occasionally and a daily window flatters a product used habitually. Vendors pick the combination that shows their product in the best light, so the metric is close to useless for comparing two companies and very useful for one company over time. Ratios extract more than the raw counts. Dividing daily by monthly gives a rough measure of how many days in the month an average user shows up, and it separates products people live in from products they visit; a low ratio is not a failure, it is a description of the product, and the mistake is chasing a number appropriate to a different category. The failure mode to watch for is drift. A definition that quietly widens, by counting a background sync, a notification open or an automated API call as activity, produces a chart that rises while the product is not being used more, and the change is usually invisible because nobody re-reads the definition. Write it down where the chart lives, version it, and annotate the chart on the day it changes, since a redefinition makes every earlier point incomparable.