Badges are the numbered red circles pinned to app icons on the iPhone Home screen. They're counters that your app displays to tally the number of waiting messages, tasks, missed calls, or other content. Badges quietly rack up their counts as new content arrives, so they provide a more subtle way to get people's attention than notification alerts. Unfortunately, they're also more ambiguous. All those little numbers sprinkled on your apps mean something, but what exactly?
A stinkin' badge is a badge that misreports its tally of new content, either showing a count for content you've already seen or double-dipping by counting certain content twice. Not all badges stink, but there are enough stinkin' badges in circulation that their overall use is compromised. Apple itself contributes to this problem with its own built-in apps. The badge on the Messages app continues to count messages even after you've read them as notification alerts upon arrival. The Phone app is even worse: when a caller leaves a voicemail message, the app's badge tallies the call twice, once for the missed call and another for the voicemail message. Even after you listen to the voicemail, the badge continues to show the count for the missed call until you specifically visit the app's Recents screen. The result is that you're often left unsure about whether there's anything behind the red-flag badges on your apps. The badges lose meaning.
Figure 10-6. The Phone app lights up its badge with "2" for a single missed call (left), once for a recent call and another for the voicemail (right). This miscount is not only misleading but obliges you to tap over to the Recents screen to clear the badge even after you've listened to the caller's voicemail message.
Other apps, like Mail, reliably get the count right, and their badges smell like roses. The principle is simple—don't double-count—but the implementation isn't always so easy. Unfortunately, apps that display notifications as alerts can't always be sure that people have seen every alert, and so they increment the badge for every item, just to be safe. The better course of action is simply to offer just one or the other, badges or alerts, but not both at the same time. If you can't offer reliable counts in your badges, don't bother with them at all. We don't need no stinkin' badges.
If you do offer badges, though, offer the option to turn them off. Even when they're trustworthy, badges come with a disquieting cognitive burden: this app has 13 widgets waiting for you, that one has 18 messages, and this other one has 23 whatzits. Instead of being helpful, these tallies sometimes overwhelm, creating the anxious incentive to bring the badges down to zero, even for content that doesn't demand priority attention. The life goal of thinking people typically consists of more than cycling through apps to mark things read, but a bevy of badges sometimes leads us to think otherwise. Let people opt out of the number game; it's not always a service.
Despite the mixed benefits of badges, they do underscore the value of passive messaging. Unlike active messages like alerts, badges deliver their message in hushed tones, letting you know that content is accumulating without interrupting you to say so. With apps, as with people, a healthy sense of humility is a big part of good manners, and polite apps do most of their work quietly without drawing undue attention to themselves. To be sure, there's an appropriate role for bold statements through alerts and notifications, but passive messaging tends to be more reliably helpful, providing real-time commentary on the app's status without getting in the way of what your audience is trying to do.