Daily active users (DAU) is the total number of users engaging in some way with a product or service in a given day. The higher the DAU of a product or service, the more successful that it is perceived to be. In almost all cases, DAU is used to measure engagement with web or mobile products and services, and it’s not unusual for those that track their DAU metric toboast about key milestones.
In most cases, all it takes for users to be considered as “active” is for them to view or open the product or service on a given day; there’s no requirement for users to fully engage with it. Many web and mobile-based businesses (e.g., Facebook, Twitter, and others) use DAU as their primary metric for measuring popularity and the potential for growth of an online platform.
DAU is also used to calculate other metrics such as monthly active users (MAU).