Messenger for Firefox lets you use Facebook right from your Firefox browser so you can continue your conversations wherever you go on the web even without opening Facebook website. You can also view your notifications, friend requests and messages by clicking the icons in the upper-right corner of Firefox.
How to enable Facebook Messenger in Firefox ?
You can enable Facebook messenger for Firefox by clicking the green button in the following page on Facebook. Enable Facebook Messenger for Firefox.I have enabled Facebook messenger in my Firefox browser and it is cool.
Facebook-Messenger-for-Mozilla-Firefox
The settings for turning off chat, notifications and sidebar are also very simple. From the top right corner you can change the settings by clicking Facebook icon.
Click on Facebook icon to change the settings for messenger
For the people who are using Mac and Linux this might be useful since Facebook has already introduced Messenger for Windows.Try this and comment how you are feeling with this.