WhatsApp is testing messages that self-destruct after you read them

WhatsApp is working on a new feature: Messages that disappear after you read them.
This is according to WABetaInfo, which found the feature in the latest WhatsApp for iOS beta, version 26.19.10.72.
According to the WhatsApp beta screenshot posted by the outlet, the feature will appear under the "Privacy - Default message timer" part of WhatsApp's settings. The user can choose to have the timer off, have the messages disappear after a fixed period of time (currently available options are 24 hours, 7 days, and 90 days), or "After reading."
According to the introductory text in WhatsApp, when "After reading" is selected, messages disappear "after they're read," while unread messages disappear after 24 hours. While that's a bit vague, the screenshots posted by WABetaInfo discover that this feature actually adds an additional timer, which kicks off after a message has been read. The options for this secondary timer are 5 minutes, 1 hour, or 12 hours.
The feature is not fool-proof, and WhatsApp adds a disclaimer that people "may find other ways to save messages." But it is the safest option yet if you want the messages to be read once, and only once, by the intended recipient.
It's unclear when the feature will become available widely. WhatsApp has previously tested the feature on Android, and now it's expanded it to iOS devices as well, signalling it may happen soon.