WhatsApp introduced disappearing messages back in 2020, but these were only intended for one-to-one chats. Now a new feature called Expiring Groups is in the works and was just discovered in the TestFlight app with WhatsApp Beta for iOS version 23.5.0.070.
As you can see in the screenshot, WhatsApp Expiring Groups are linked under the group settings. You can set the expiration time to a day, a week, or a custom date. Even if you can find the new feature under the group settings, it still only applies to your own messages. So unless the other participants in the group have set expiration dates, they remain in the group and their messages remain viewable.
You can also change your mind at any time and delete the expiration date. And even if you forget that, WhatsApp will prompt you to confirm that you want to permanently delete the messages. The new feature could prove to be a useful tool for decluttering your WhatsApp account. Old groups that are no longer relevant would be automatically deleted and the storage space used would be released.