https://www.cnbc.com/2019/02/05/how-to-delete-messages-on-facebook-messenger.html

Facebook on Tuesday is launching a new feature that lets you delete old messages inside its chat platform, Facebook Messenger. It's a feature that previously only CEO Mark Zuckerberg had.

If you've sent messages you might regret, or if you just want to clean up older chat history, you can easily delete select messages.