App Store Connect Shared Secret

Server validation, also known as server-side receipt validation, is a process used to ensure that purchases made within an app are authentic. This is achieved by using an encrypted file, in PKCS#7 format, which contains information about all in-app purchases. To authenticate purchased content, you can include receipt validation code in your app or server. App Store receipt validation involves sending a request to Apple's servers to verify the purchase and determine whether it was valid. This is particularly important for auto-renewable subscriptions as you need to know when they expire in order to provide or block access to your content. Receipt validation is also used when users need to restore a purchase, such as when they reinstall your app.

Developers can use Apple's StoreKit framework to incorporate in-app purchases (IAPs) into their apps on iOS, macOS, watchOS, and tvOS. The framework facilitates secure payment processing on behalf of the app, connecting with the AppStore and requesting user authorization for payments.

In iOS, developers can enable users to purchase additional features or content within an app using in-app purchases, providing a way to monetize their apps beyond the initial purchase price or to offer a "freemium" model. Apple manages the payment process and deducts a commission, known as the "Apple tax", from the sales amount.

In-app subscriptions are a payment model in which users are charged on a recurring basis in exchange for access to premium content, exclusive features, or services. They are frequently used by developers as a way to monetize their apps by providing users with ad-free experiences or exclusive content.

An In-app purchases SDK (Software Development Kit) is a set of tools, code libraries, and documentation provided by a developer platform, such as Apple or Google, that allows app developers to integrate the ability for users to make purchases within their app.