The feature is launching on Messenger across all supported devices and countries today, but its Instagram release will take some time yet. Regardless, here’s how it works: when Vanish Mode is enabled in a group or one-on-one conversation (you swipe up on your screen to turn it on), the feature will automatically erase texts, photos, stickers, emotes, and other forms of media.
However, this doesn’t happen on a timer, like some other similar solutions. Instead, the messages only erase themselves when your conversation partner (or partners) has seen them, and you’ve closed the chat.
If you keep the chat open, the messages will remain. To switch the feature off, you just press the “Turn Off Vanish Mode” button that will appear at the top of your Messenger window.
However, you can’t force other users to enter Vanish Mode with you. Once you or someone else enables it, everyone has to opt-in for the mode to be turned on. If one user opts out, you can’t use the feature in that chat unless you try again at a later time.
Vanish Mode reportedly will work much the same way over on Instagram, thanks to Messenger’s deep integration on that platform.