While most of our conversations on WhatsApp are with friends and family, we also use it quite often to talk to people we don't know (e.g. a store). Since we don't need to store these kinds of conversations forever, it's better to send disappearing messages to recipients.

WhatsApp offers a self-destructing feature for chats. When you enable it for a specific group or private chat, messages are automatically deleted from your phone and the recipient after a week. Here's how to set it up.
First, make sure you have the latest version of WhatsApp on your phone from the Play Store on an Android device and the App Store on an iPhone.
Now, open the “WhatsApp” app on your iPhone or Android device and enter the group or private chat you want to set to self-destruct in the “Chats” tab.

Tap the recipient's or group's name at the top of the conversation to visit their profile .

Select “Disappearing messages”.

Note: In a group chat, only admins have the right to set this setting.
Turn the option “On” to enable disappearing messages in this conversation.

Now, any text or media sent in this conversation by you or the other person will be deleted after a week.
However, messages sent before this change will not be affected. You can turn off the disappearing messages feature by doing the reverse setting.

When enabled, WhatsApp will notify the recipient and add a tiny clock icon above the chat image thumbnail

Please note, however, that this does not prevent chat members from taking screenshots of chats or backing up media elsewhere. Additionally, the option to export the chat will still be available.
Therefore, WhatsApp's self-destruct feature is strictly only for regularly clearing inbox of unnecessary messages, not for private and confidential conversations.
Source: howtogeek.com
