An app makes the list when its own company has published how many people use it, and that number puts it among the largest apps in its category. Every figure comes from the company itself: an earnings release, a shareholder letter, a filing or its official newsroom. Numbers that only appear in news stories, app-store trackers or roundup sites are left out, and so are apps whose makers have not shared a figure in the last two years.
Most companies report users across all their devices, not just phones, so the numbers cover each service as a whole. Some figures cover a company's whole platform rather than one app; the metric says so where that applies. A daily user count is not the same as a monthly one, so the default order is a rough guide rather than a strict ranking.
The database is checked every day. When a company publishes a newer figure it replaces the old one, broken source links are fixed, and apps whose figures go stale are removed. Spotted something out of date? Tell us on the contact page and see our corrections log. App names are trademarks of their owners; this page is not affiliated with any of them.