Which feature in iOS allows for quick replies to notifications without opening the app?

The feature that allows for quick replies to notifications without the need to open the app is found in the Notification Center. When a notification appears, users can interact with it directly from the notification itself, enabling them to respond swiftly. This is particularly useful for messages and alerts, allowing for seamless communication without disrupting workflow by switching applications.

Notification Center gathers all notifications in one place, and with the implementation of interactive notifications, users can take immediate actions—such as replying to a message—right from the notification banner.

Widgets, while useful for providing glanceable information and quick access to certain app functionalities, do not provide the direct interaction that notifications do. The Control Center is primarily designed for quick access to settings and tools like Wi-Fi or screen brightness, and does not deal with notifications in the same way. 3D Touch, which provided pressure-sensitive touch interactions, has been largely replaced by other features in recent versions of iOS, and while it offers a form of quick interaction, it is not central to the immediate notification reply functionality.