Mobile check-in apps are digital tools that allow users to check in for flights, hotel stays, or events using their smartphones. These apps streamline the process by enabling users to confirm their arrival and receive boarding passes or room keys without waiting in long lines. Many airlines and hotels offer their own mobile check-in apps, making it convenient for travelers to manage their bookings. Users can often access additional features, such as flight status updates or room preferences, enhancing their overall experience while saving time and effort during their travels.