This unofficial app (browser addon) is a wrapper to the original Messenger application and tries to make it usable as a browser plug-in.
An easy-to-use and lite app for messenger
App for Messenger™ (Facebook™ Messenger) is the easiest way to open and use Messenger from your desktop machine (PC, MAC or Linux). Clicking on the toolbar button, renders Messenger in a standalone UI. Moreover, the window is re-sizable to your desired choice and all the changes are auto saved to the memory. Note, to start using this App, you need to have a Facebook account.
App for Messenger™ is considered a very lite Addon and does not add any additional burden to your browser. Moreover, the popup has a built-in “Always-On-Top” feature which makes the window remain always on top of other windows, and enables you to do multi-tasking.