The reopen window
If a visitor writes again soon after you resolve a conversation, the same conversation reopens. It goes back to the original owner if they’re still online, and it doesn’t use another conversation from your monthly quota.
Set the window in Chat settings › Appearance under Reopen window — 24 hours by default. 0 means resolved conversations never reopen.
After the window, a new conversation starts and is tagged as returning.
History stays together
When a returning visitor starts a new conversation, the inbox shows their earlier conversation above it, separated by a line. Click Show earlier conversations to go further back. The visitor sees one continuous chat history.
One open conversation per visitor
A visitor never has two open conversations at once. If they start one in each of two browsers or windows, the two are merged automatically: the one with the latest message stays open, the other is marked resolved, and both get an internal note explaining what happened.
Remember me
By default a visitor’s chat stays connected for 24 hours after their last activity on that device. If you allow it in Chat settings › Privacy, visitors can choose to be remembered for 30 days.