In July, Microsoft officials said the company had hit the 13 million daily active user (DAU) milestone for its Teams group-chat service. On November 19, officials said that number is now at 20 million.
Teams' biggest rival Slack passed 12 million daily active users in October 2019. Slack has been trying to make the case that not all user numbers are created equal, citing "deep engagement" among its DAUs as evidence of its significant market penetration. Among its paid customers, Slack said users spend more than 9 hours a day connected to its service, including spending around 90 minutes per day actively using the platform. Microsoft has not released any kind of Teams engagement metrics, as far as I know.
Update: A Microsoft spokesperson said the company did share some new engagement metrics today, specifically that Teams customers have participated in more than 27 million voice or video meetings and performed over 220 million open, edit, or download actions on files stored in Teams.
The spokesperson added that Microsoft defines DAU as "the maximum daily users performing an intentional action in the last 28-day period across the desktop client, mobile client and web client." Examples of an intentional action includes starting a chat, placing a call, sharing a file, editing a document within teams, participating in a meeting, etc. Microsoft does not count "passive actions like auto boot, minimizing a screen, or closing the app" in calculating DAU. In addition, the company "de-dupe(s) all actions across a single user ID."
In March 2019, when Teams turned two years old, Microsoft officials said the product was being used by more than 500,000 organizations worldwide. Microsoft did not start providing daily active user data for Teams until July this year.