If someone sends you a message when you're signed in to Hangouts, a Hangout window will appear. To respond, type your message in the text box and press Enter.
Receiving messages from someone for the first time
If you are signed in
You'll automatically receive the message if the sender is in a group that can contact you. In the Hangouts invite settings
, you can choose whether someone can contact you if they know your phone number, know your email address, or are in your Google+ circles.
If the sender isn't in any of these groups, you'll receive a Hangout invite.
If you aren't signed in
If someone sends you a message for the first time while you’re offline or signed out of Hangouts, you'll receive an email and a Hangout invite
. The email will include information about who wanted to Hangout with you.
Receiving messages in other situations
If someone sends you a message when you’re offline, signed out of Hangouts, have mute or snooze notifications turned on, or have notifications for that Hangout turned off, the message will appear bolded at the top of your Hangouts list until you read it. When you click the message, a Hangout window will open and you can reply.
Read up to here indicator
When someone sends you a new message, you can let the person know you have seen it by clicking your Hangout window. When you click your Hangout window, your profile image will show under the message the person sent. Closing or minimizing your Hangout window will not cause your profile photo to appear.
Status next to 'Read up to here' indicator
If your contact is using the Hangouts app version 2.0 and above on Android, their status will briefly appear next to the "Read up to here" indicator when you first open the conversation.
To see the contact's status again, you can touch the "Read up to here" indicator and the status will display.