One of the features Facebook which users of this Social networks I love him and hate him to the same extent is the notification Seen who warn those who send private messages (Facebook Chat or Messages) whether they were or not read. While this feature It can be useful for those who send the messages, those who receive those messages most likely would like to block this notification for various reasons (either they do not have time to respond at that time or do not want the message to find out that it has already been read, etc.), so that it is no longer displayed when the messages are read.

Desi Facebook It does not allow users to disable this feature from network settings, there are methods by which users can block SEEN notification to be displayed when reading messages, such a method being the use of extensions Facesnoop or Facebook Chat Privacy For Google Chrome browser.
Facesnoop Prevents both Facebook and users who have sent messages to find out if they have already been read (although users will be able to read the messages received as before the extension installation, they block Facebook to check if the messages have been read and so will not display SEEN notification). In addition, the extension is activity Immediately after installation, the browser is not necessary to restart.

Facebook Chat Privacy It acts similar to the extension Facesnoop, this blocking, besides SEEN notification and the status ”is typing"Displayed when users respond to the messages received.

Download Facesnoop (Chrome Extension).
Download Facebook Chat Privacy (Extensie Chrome).
Note: Facesnoop and Facebook extensions Chat Privacy works only on the Chrome browser; If after installing one of the two extensions you will access Facebook from another browser or other device, the SEEN notification will be displayed when reading the messages received. For other browsers (Firefox, Opera and Chrome) you can install the extension Social Revive, and for Facebook Mobile you can install the application Privy Chat for Facebook (Android) or the application Unread (iOS).
STEALTH SETTINGS – How to block Seen notification in Facebook Chat/Messages