WhatsApp makes changes to privacy controls on Android devices1
To enable it, you'll have to go to Settings in WhatsApp, then tap Accounts / Privacy / Groups and select one of three options: Everyone, My Contacts, or My Contacts Except. Well, the third option has been added today and replaces the “Nobody” option which was originally added back in April.
The changes are based on feedback from users during WhatsApp's initial rollout to give them even more control over the contacts that they don't want to receive messages from. The new My Contacts Except option lets users choose to exclude specific contacts or “select all.”
WhatsApp announced that the update that contains the new changes is rolling out to Android users worldwide this week, so if you're seeing a new version of WhatsApp in the Google Play Store, then you should have the new feature available after you update.