Monthly active users
How many people opened an app at least once in thirty days, which is a lower bar than it sounds.
Monthly active users, or MAU, counts everyone who used a product at least once in the past thirty days. It is the number technology companies reach for when they want to show scale, and it is the number you should read most carefully. Opening an app once counts exactly the same as using it every day, so MAU tells you about reach, not about habit or satisfaction.
Two things are usually missing from the announcement. First, paying subscribers, which is a much smaller and much more revealing figure. Second, how the users arrived. An assistant that is built into a phone, a search engine and an email client will collect users who never went looking for it, which is a genuine business advantage but makes comparison with a product people had to seek out unfair. When ChatGPT and the Gemini app both passed a billion monthly users in 2026, the headline was real and the like-for-like comparison was not.