Why Teams uses so much CPU and memory
- Video meetings: encoding your camera and decoding everyone else's, continuously.
- Background effects: blur and virtual backgrounds analyse every video frame.
- Screen sharing, which captures and encodes your screen on top of the video.
- Busy chats and channels with lots of images, GIFs and previews.
- Several accounts or organisations signed in at once.
What helps the most
- Turn off background effects before or during a meeting, in the meeting's video or background settings. This is usually the biggest saving.
- Turn off incoming video in large meetings when you only need to listen. Look for it in the meeting's More menu.
- Stop sharing your screen as soon as you're done presenting.
- Close other heavy apps and browser tabs during calls.
- Keep Teams and macOS updated, since performance fixes ship regularly.
- Quit Teams fully from its menu (or with ⌘ Q) at the end of the day, instead of only closing the window.
Teams is slow even outside meetings
Check Activity Monitor's Memory tab. If memory pressure is yellow or red, Teams is competing with everything else you have open; closing other apps helps more than any Teams setting. Signing out of organisations you don't use also reduces the load. As a test, try Teams in a browser for a day and compare.