If you are looking to block a pesky or chatty contact on Facebook Messenger, the app offers a very simple way to do so.
As part of the blocking feature, you will not only appear as invisible to your blocked contacts, Facebook Messenger will also notify you each time you attempt to join a group conversation that involves any of your blocked contacts.
How To Block Someone on Facebook Chat
Open Facebook Messenger and search for a conversation with the person you would like to block. Tap on the small blue exclamation mark displayed at the top-right corner of your screen to display the Details page. Tap on Block:
Next, toggle the Block Messages switch to On:
Your contact is now blocked on Facebook Messenger.
It is important to note that blocking someone on Facebook Messenger is not the same thing as blocking somebody on Facebook. Unless you completely block a contact, blocked Messenger contacts will still have access to your Facebook profile, and all of its platform functionalities. That said, in blocking someone on Facebook Messenger, you are removing their capability to see when you are using the chat application, thus preventing them from calling or messaging you.