You can delete messages just for yourself or request that messages be deleted for everyone.
Delete messages for everyone
Deleting messages for everyone allows you to delete specific messages you’ve sent to an individual or group chat. This is particularly useful if you sent a message to the wrong chat or if the message you sent contains a mistake.
Messages that are successfully deleted for everyone will be replaced with:
“This message was deleted“
To delete messages for everyone:
- Open WhatsApp and go to the chat containing the message you want to delete.
- Tap and hold the message. Optionally, select more messages to delete multiple messages at once.
- Tap Delete > Delete for everyone.
- In order for messages to be successfully deleted for everyone, you and the recipients must be using the latest version of WhatsApp.
- Recipients using WhatsApp for iOS may still have media you sent saved to their Photos, even after the message is deleted from the WhatsApp chat.
- Recipients might see your message before it’s deleted or if deletion wasn’t successful.
- You won’t be notified if deleting for everyone wasn’t successful.
- You only have about an hour after you’ve sent a message to request to Delete for Everyone.
Delete messages for yourself
You can delete your copy of messages you’ve sent or received from your phone. This has no impact on your recipients’ chats. Your recipients will still see the messages in their chat screen.
To delete messages for yourself:
- Open WhatsApp and go to the chat containing the message you wish to delete.
- Tap and hold the message. Optionally, tap more messages to delete multiple messages at once.
- Tap Delete > Delete for me.
Source : https://faq.whatsapp.com/