Matthew Green:

If you install WhatsApp, Facebook Messenger, Signal, Snap or even Telegram(please don’t!) you’ll encounter a simple feature that addresses this problem. It’s usually called “disappearing messages”, but sometimes goes by other names.

I’m almost embarrassed to explain what this feature does, since it’s like explaining how a steering wheel works. Nevertheless. When you start a chat, you can decide how long the messages should stick around for. If your answer is forever, you don’t need to do anything. However, if it’s a sensitive conversation and you want it to be ephemeral in the same way that a phone call is, you can pick a time, typically ranging from 5 minutes to 90 days. When that time expires, your messages just get erased — on both your phone and the phones of the people you’re talking to.

A separate feature of disappearing messages is that some platforms will omit these conversations from device backups, or at least they’ll make sure expired messages can’t be restored. This makes sense because those conversations are supposed to be ephemeral: people are clearly not expecting those text messages to be around in the future, so they’re not as angry if they lose them a few days early. [...]

To recap, nearly every single other messaging product that people use in large numbers (at least here in the US) has some kind of disappearing messages feature. Apple’s omission is starting to be very unique.

I do have some friends who work for Apple Security and I’ve tried to talk to them about this. [...] When I ask about disappearing messages, I get embarrassed sighs and crickets. Nobody can explain why Apple is so far behind on this basic feature even as an option, long after it became standard in every other messenger.

I can only speculate why iMessage doesn’t offer this feature. Perhaps Apple doesn’t want to imply that “disappearing messages” are in any way guaranteed to be ephemeral, which would be impossible. Who’s to say the recipient hasn’t screenshotted them? And if Messages were to impose a software block against capturing a screenshot of a “disappearing message” (like the way you can’t capture screenshots of DRM-protected video), who’s to say the recipient hasn’t used another device to take a photograph of the display showing the ostensibly-ephemeral message? E2EE is a mathematical guarantee. There’s no way to offer such a guarantee regarding ephemerality, and perhaps that gives Apple pause.

But I think that would be letting a desire for perfection get in the way of offering a feature that’s useful and good enough. People who use disappearing messages on other platforms — and as Green points out, all of iMessage’s rivals offer the feature — understand the risks. Vanishingly few people understand the difference between “encrypted in transit” and “end-to-end encrypted”. But just about everyone intuitively understands that even a “disappearing message” might be screenshotted, photographed, or otherwise recorded. There’s an implicit trust between sender and recipient.

The other angle I can think of is complexity. Messages is one of Apple’s most-used apps, and in many ways it exemplifies Apple’s approach to software design and computing in general. Where critics see an app that is popular despite offering fewer features than its rivals, Apple (and I) see an app that is popular and beloved to some degree because it offers fewer features. All new features necessarily add some complexity, and disappearing messages would add quite a bit. Can you have two chats with the same person/group, one standard and one ephemeral? If so, now you’ve raised the specter of accidentally sending what’s intended to be a disappearing message to the non-ephemeral chat with that person or group. If not, how do you send a brief disappearing-message exchange with someone with whom you have a long archive of messages you want to keep forever? (Perhaps the idea of private browsing in Safari could serve as an inspiration for disappearing messages in Messages — an entirely separate mode with a distinct visual state.)

The basic idea of disappearing messages is pretty trivial and easily understood. A good design for implementing them in Messages is not trivial. Solving these hard design problems is what makes Apple Apple, though. They’ve added some rather superficial features to Messages (Genmoji and message effects for example), so I agree with Green that they ought to tackle disappearing messages and that surely they can find a way to do it where the added complexity doesn’t create confusion. It’s a hard challenge, to be sure, but a worthy one. Apple’s designers could really have some fun with this too, with novel ways to present “disappearingness” visually.