HelpCrunch offers a variety of communication management tools and features to help you manage your customer interaction smoothly and effectively.
A green circle next to the username in All chats, My chats and Contacts sections of your account will hint you on who is active at the moment and can be reached right away.
Note that if the user is online, your chat messages might still remain unread, until the user opens the chat window on your website and actually reads them. That explains the case when you see the green circle, but your messages remain unseen for a while.
If your user is offline, you can add the "Last seen" column to your table via the "Edit columns" button.