Facebook messenger is a trully battery and data consuming app by Facebook.In now a days we are forced by Facebook to install this app for chatting purpose.
I don't know why Facebook doing this, now you when going to chat you are required to install this app but when there is option for direct chat with fb app then why we download this one.
With this messenger app a high space is consume in your valuable mobile space, which is a problem in low memory devices and because of this app your battery drains faster because Its runs all the time in background.
Some feature is good but no need Because it also available in Facebook.
