The news from WABetaInfo Twitter channel, a source of early WhatsApp news and speculation, which claims to have discovered the feature in the WhatsApp 18.104.22.1689 beta build for iOS.
In the video tweeted by WABetaInfo showing the message deletion process in action. By tapping and holding on a sent message to bring up a list of options, including “revoke”, which can be selected to delete the message from the conversation. It also seems that this can be applied to read messages, as WhatsApp’s blue check marks can be seen briefly before the messages are removed.
A tweet reveals an “edit” option available in the same menu, which would allow users to amend the content of sent messages. WABetaInfo says would be disabled by default.
— WABetaInfo (@WABetaInfo) December 14, 2016