When you’re working on a file in Google Drive, you can communicate with others working on the same file, and you can all collaborate on the file in real time. If you and a partner are drafting a document with Google Docs, for example, the two of you can chat about your progress and make edits to the document simultaneously.
When you’re viewing or working on something in Google Drive and somebody else opens the same file, you’ll see his or her Google+ profile picture appear in the top-right corner of your browser window. (If the person doesn't have a Google+ profile picture, you'll see their first initial. If the person's viewing the item anonymously, they'll be assigned an animal name and image.) As more people open the document, more profile images appear. If you hover over a profile image, you’ll see information about the viewer pulled from his or her Google+ profile, and you can add the person to one of your Google+ circles with a click.
To begin a group chat with everyone viewing the document, click the Chat button, which you’ll find in the top-right corner of your window. A chat box will appear at the bottom of your file, and everyone who’s viewing the document and who’s signed in with a Google account will be included in the group chat.
If you're using Sheets, you'll see the legacy chat experience. Instead of seeing distinct profile images in the top-right corner of your window, you'll see a colored tile for each other person viewing the document. If you click the tiles, a sidebar will appear where you'll be able to chat with the group of people viewing the spreadsheet.
By default, incoming chats are accompanied by a dinging sound. To mute the chat, open the chat box, click the gear icon in the corner, and uncheck the checkbox you’ll see in the dialog that appears. This will turn off the notification sound for chats across Google products, including Gmail and Google+.
Drive chat compared to chat in other Google products
Drive’s group chat box may look like the chat experiences you know from other Google products, like Gmail and Google+, but there are some differences. With Google Chat in Gmail and Google+, for instance, you can have multiple chats with individual people. In Drive, you can have only one group chat, which will include the people viewing the file you’re viewing.
If you’ve chatted in Gmail and Google+, you may have noticed that a chat started in Gmail will carry over into Google+, and vice versa. The same isn’t true for chats in Google Drive. Chats you start in Google Drive won’t carry over into other Google products, and chats you start in other products won’t appear in Google Drive.
If you’re using Google Docs, Sheets, Slides, Forms, or Drawings, you and others with access to a file can make edits to that file at the same time. In Docs, Sheets, Slides, and Drawings, you’ll be able to see what others are up to keystroke by keystroke, and they’ll be able to see what changes you’re making as you make them.
Real-time collaboration is available only when you and your collaborators are online.