Weekly Active Users (WAU)
The number of unique users that engage with your app within a 7-day window. WAU is generally used by businesses where users are expected to interact with the app at a weekly frequency (e.g. analytics tools).
Active users are individuals who engage with your app over a given time period. This could be making a transfer (online banking), adding to cart (ecommerce), downloading or logging into the app (SaaS) — or really any activity that meets your company’s definition of "active" user activity.
WAU is the metric used to track weekly user engagement, including new and existing users.
You can identify your app’s weekly active users through a personal unique identifier like email addresses, IDFA (for consenting iOS 14+ users), and user IDs. In fact, app marketers often use a combination of these as backup in case one fails.