Google Chat has replaced Hangouts in Gmail. During the transition, you can access Hangouts at hangouts.google.com.
What You Should Do
- If you do not use any chat features, you don't need to do anything.
2. For group messages, create new groups in Chat or use the rooms feature.
- Learn about the differences between group messages and rooms.
Directions and Tutorials
How to use Google Chat in Gmail.
Google Chat Help Site