https://www.theverge.com/2018/11/7/18071376/facebook-messenger-unsent-message-10-minute-time-limit

Facebook Messenger will soon allow you to delete sent messages up to 10 minutes after you’ve originally sent them. The feature is listed as “coming soon” in the release notes for version 191.0 of Messenger’s iOS client. Compared to the hour Facebook gives you to delete an erroneous WhatsApp message, 10 minutes doesn’t give you too much time to correct yourself. But it’s a lot better than having your mistakes preserved eternally.

Messenger’s “unsend” functionality has been on the cards since April, after Facebook admitted that it had been quietly deleting messages sent by its CEO Mark Zuckerberg. The functionality was first spotted in October during testing.