Overview
Microsoft Teams is a teamwork collaboration service that includes chats, video calls and file sharing. While each feature has many independent service limits, there are some common questions about the limits with the Chat and Video Calling functionality.
Details
How many participants can be in a meeting?
For active employees and students the maximum number of meeting participants is 20,000. The first 1,000 participants can fully interact in the meeting and any connections over 1,000 are put into "view-only" mode.
How many participants can be in an ad-hoc chat meeting?
The maximum number of participants in a custom chat is 20.
Additional Resources
Microsoft has more technical information on the service limits available here: https://docs.microsoft.com/en-us/microsoftteams/limits-specifications-teams