Daily Active Users (DAU) is a key metric used to quantify the number of unique users engaging with an app or site daily, with its calculation varying significantly between companies due to different definitions of "user" and "action." DAU is critical for assessing product stickiness and growth potential, frequently appearing in discussions about technology IPOs, as it indicates how many people find an app useful enough to use regularly. However, relying solely on DAU can be misleading, as high numbers do not necessarily equate to valuable user engagement, making it important to consider additional metrics like Monthly Active Users (MAU) and Average Daily Active Users (ADAU) for a more comprehensive understanding of user behavior. The metric is particularly relevant in contrasting scenarios, such as comparing a B2B security software with a social media platform like Facebook, where barriers to entry and definitions of actions vary, leading to incomparable DAUs. To maximize the utility of DAU, it should be analyzed alongside indicators of value, such as in-app purchases or content engagement metrics, using robust analytics platforms to gain deeper insights into user behavior and app growth strategies.