According to WABetaInfo, the latest beta version of WhatsApp for iPhone allows a restricted subset of users to edit messages. The feature works similarly to what is already in the Android beta, where users may just press a message and tap the “Edit” button.
Unlike Telegram, though, WhatsApp will limit how users can edit sent messages. Users, for example, will only have 15 minutes after a message has been received to change it. The method is similar to that of iMessage, which has a 15-minute time limit for modifying messages.
Unlike iMessage, which displays a history of revisions to other users, WhatsApp simply displays a “modified” label on messages that have been edited by the sender. In this situation, the technique is more akin to Telegram. Another thing to remember is that the edit option only works for text messages, not image, video, or document captions.
There is no word on when WhatsApp intends to make this capability available to the general public. However, given that the feature was only recently offered to WhatsApp beta for iPhone users, the formal rollout might happen very soon.