How one developer built a Web-to-iOS app login handoff that bypasses Apple's payment cut

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A developer has detailed a system that lets users pay for an app via a web funnel and then open the iOS app already authenticated, even before it is installed. The approach avoids Apple's in-app purchase commission by processing payments entirely on the web, then using a one-time login token to authenticate the user on first app launch. The token is passed to the app using AppsFlyer's deferred deep linking, which survives the App Store installation barrier. A key technical hurdle on iOS was that since iOS 14.5, only a restricted set of deep link parameters are passed to fresh installs, causing custom token fields to be silently dropped. The developer's fix was to place the token inside one of AppsFlyer's explicitly permitted parameter slots, such as deep_link_sub1, rather than a custom query parameter.

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