Some iPhone apps display a badge -- a circle containing a number -- on the corner of the app icon. A badge usually indicates new content within an app, such as a new message in a text app, but apps can use badges for other purposes, such as to indicate missed calls. Apps that support push notifications update their badges without being opened, while badges that rely on online data require either a Wi-Fi or cellular connection to update.
Types of Notifications
Apple iOS 7 provides apps with several methods to display notifications. For notices that need to grab your attention immediately, apps can display pop-up alert messages, display banner notices at the top of the screen or play an audible alert sound. Badges serve a purpose similar to these notifications but without behaving as intrusively. App badges show up silently and won't interrupt your work, and unlike alerts and banners, you never need to dismiss a badge. As soon as you view the content related to a badge within an app, the badge disappears automatically.
Uses for Badges
Badges provide different information depending on the app. Among built-in iPhone apps, the Phone app displays a badge indicating the number of missed calls, the Messages app has a badge that counts unread texts and the App Store app's badge states the number of updates available for installed apps. Most apps installed through the App Store use badges in similar ways. The Podcasts app badge, for example, counts new episodes, while the Gmail app has a badge for unread emails, which you can customize to count either all new messages or only those in your primary inbox. Some apps have highly customizable notification settings, such as Twitter, which has toggles for counting mentions, direct messages and even tweets from specific users in the badge; a badge appears to count whichever notification type you select.)
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Aside from counting information inside apps, the iPhone has special uses for badges on folders and on apps with errors: Each folder displays a badge that indicates the sum of all badge numbers on apps within the folder. When an app encounters an error, such as when an email fails to send, you may see a badge with an exclamation point.
Even if an app doesn't provide its own notification or badge options, you can turn its badges off in the system's Settings app. Tap "Notification Center" and choose the app from the list. Switch off "Badge App Icon" to disable an app's badge. To completely stop an app from creating notifications, change its alert style to "None" and switch off every slider on its page. The iPhone doesn't have a toggle to turn off badges on every app simultaneously, but you can temporarily hide all new notifications by entering Do Not Disturb mode: Swipe up from the bottom of the screen and tap the moon icon.