If you are tired of clearing and sorting your message box one thread at a time, then this hack is just for you.
For all the irrelevant messages and annoying spams you get, I bet you always wished that you could have a single button wipe all facility.
This Google Chrome Extension lets you wipe your message box in a single click.
This hack works only on PCs for now.
Before erasing your entire messaging history, we recommend you to make a Backup of your Facebook data beforehand because this procedure is a permanent one.
Once erased; messages cannot be recovered, so try to be as careful as you can.
To get you started, the first thing you need to do is, download the Facebook Delete All extension from the Webstore.
Once the download is done, add it to your Google Chrome extensions.
After adding the extension when you open your Facebook Message window, a dialogue like this will appear asking for you to begin the deletion process.
Click on Begin Deletion and let out a sigh of relief as you watch the messages disappear.