How to delete all facebook messages at once?
Very simple and fast! Delete Messages on Messenger will help you in this.

To delete all messages, you just need to do
1. Login to your Facebook account
2. Choose the type of your conversation chat
3. Choose messages, then click delete

Delete Messages on Messenger in a short time will automatically remove your selected Facebook messages.
You only need to relax and enjoy the result.

* Warning:
- Using this app can make your account locked temporarily (checkpointed by Facebook), please don't use it if you don't know how to unlock your account, consider before installing. Thank you very much!