Google Talk (Jabber) features something known as invisibility which makes the user seem to be offline, but really is online. This is a popular feature among most IM networks. However, is it possible to figure out if someone is really offline or just using invisibility just to avoid talking to you on Google Talk? The answer is yes.
So how did I identify when David in the conversation above was invisible or offline?
Step 1: Take the chat off the record. If you are using chat inside Gmail, this can only be done when both users are online. In clients like the official Google Talk client, the chat can be taken off the record anytime.
Step 2: When your friend is shown as offline, send them a message.
Step 3: If they are invisible, it will send normally. However, if they are offline, the server will bounce an error message saying that they did not receive your chat or cannot receive messages right now.
Why Does This Work?
Sending a chat message when a user is offline uses Offline Messages and therefore requires that the Chat is being recorded. If its not being recorded, then the other user won’t receive your offline messages.
However, if they are invisible, they will still receive your messages.
So if you ever find your friend randomly signing off for some reason, just try these simple steps!