6

What's this newly-appearing-never-seen-before thing in Facebook Chat:

enter image description here

7

Seen means that your message was loaded to the browser AND was visible to the user. If the tab was minimized or inactive at the time that the message was sent the message will not be marked as seen.

Messages are marked as seen through AJAX in a javascript function. I traced the function call, and it is being made somewhere on line 221 of http://static.ak.fbcdn.net/rsrc.php/v2/yz/r/7wj8FiAwzjS.js. Of course it is minified javascript so it is relatively hard to read.

If you are looking to disable the feature, a chrome extension has been created called Facebook Unseen.

| improve this answer | |
1

Seen means that the person you sent this to, has read the message.

Well, literally speaking, it just means that the user has opened the message page, or chat window and the message you sent has been loaded to his browser.

| improve this answer | |