The .pkpass file extension represents a digital pass used in Apple Wallet (formerly Passbook) on iOS and watchOS devices. These passes can store a variety of information, including coupons, boarding passes, event tickets, store cards, and loyalty cards. The file itself is a compressed archive (ZIP) containing JSON data, images, and a signature file. The JSON data defines the structure and content of the pass, such as the barcode, relevant dates, and display text. Images are used for the pass's logo, background, and other visual elements. The signature file ensures the pass's authenticity and prevents tampering. When a user adds a .pkpass file to their Apple Wallet, the Wallet app parses the data and displays the pass in a user-friendly format. The pass can then be used for its intended purpose, such as scanning a barcode at a store or presenting a boarding pass at an airport. Updates to the pass, such as changes to the balance of a loyalty card or a gate change for a flight, can be pushed to the user's device via Apple's Push Notification service.