This video discusses using the number of daily active users as a growth metric.

Investors closely monitor the number of active users for social media and other online platform companies. Thus, companies such as Facebook and Snapchat disclose the number of daily active users, which is the number of people that use their website and mobile app on a daily basis (Twitter discloses the number of monthly active users). Tracking the number of active users is believed to be useful in forecasting revenue growth.