What Is the Line Below the Battery Icon on iPhone Lock Screen?

The line below the battery icon on iPhone lock screen indicates the presence of the Control Center. This subtle UI element appears when Control Center is enabled, signaling users that a swipe from the top-right corner can access quick controls. Apple introduced this feature as part of its Liquid Glass design system, enhancing visual feedback without cluttering the interface. The line is a minimal yet functional indicator, helping users quickly identify available gestures. It reflects Apple's design philosophy of subtle, intuitive interactions that support customization without overwhelming the user experience. This element is visible only when Control Center is active, making it a dynamic part of the lock screen rather than a static design choice.