13 September 2021
UPDATE (August 3rd, 2021):
WhatsApp's View Once feature for photos and video sharing is now available for iPhone users. It is available with the latest WhatsApp for iOS update i.e. version number 2.21.150 or higher. You should see the "1" icon next to the caption field while sharing a photo/video if the feature is available on your device. Tapping on the icon will enable the View Once mode and that particular media file will get deleted automatically once it has been viewed by the recipient.
Original (July 1st, 2021)
WhatsApp is started beta testing a new privacy feature called View Once. It is the same feature that was first spotted last month alongside a couple of others. It will allow users to send photos and videos that can only be viewed once by the recipient. These files will get deleted automatically later on. It is an extension of the 24-hour disappearing mode that is also under testing.
View Once beta release is currently limited to WhatsApp Android users. To be specific, it is accessible on WhatsApp Android beta version 22.214.171.124 or later. The rollout is happening with randomly selected beta testers. It means even if you are running the relevant app version, you might still not get the feature straight away and will have to be patient.
If you have the feature, you will see the View Once icon while sharing a media file. The icon has number 1 enclosed in a circle with one half in solid lines and another half in dotted ones. Tapping on the icon will change its color to Green suggesting that the view once mode is now enabled. It will be grey-ish when disabled.
All media files sent using this mode can be opened only once and will disappear soon after. WhatsApp will also notify you whenever the recipient opens the file. If you have read receipts disabled, you will not be able to check when did recipient open the file but no such restriction is in place for media shared in groups.
Even though WhatsApp's aim is to improve privacy through this feature, it does not come with screenshot protection. It means the recipient can still choose to screenshot the photo and you will not get notified about it either. This is pretty much how the View Once features for the time being. If the team makes any changes or expands the beta testing to iOS, we will keep you posted.