Universal Links, App Links and Deferred Routing Build

The most common broken app link we are handed is a single line: assetlinks.json carrying the SHA-256 fingerprint of the upload key rather than the key Play App Signing actually signs the release with. Android then verifies nothing, the link opens a browser, and the campaign that paid for the click bought a web session instead of an app session. Second most common is an apple-app-site-association file served through a redirect or with a content type Apple will not accept. Both are twenty-minute fixes that sat broken for months because no engineer owned the file. What gets built: A link contract first. One routing function in the app that takes a URL and returns a destination, with every parameter named and typed, and a defined fallback for each failure it can meet: app not installed, user not signed in, content deleted, region locked, deferred payload missing. Everything else hangs off that one function. Then the hosting: apple-app-site-association using components-based paths, assetlinks.json carrying the correct release fingerprints for every flavor you ship, both served with headers that survive your CDN, and monitored so a caching change does not quietly break attribution again in March. Contexts, not browsers: We test by context, because context is where links die. Universal Links do not open from a same-domain page navigation, from most in-app webviews, or from a JavaScript-initiated redirect. Instagram, TikTok, Gmail and Slack each behave differently from Safari, and a creator campaign lives almost entirely inside the ones that behave worst. Delivery includes a run of the full matrix on real devices with a pass or fail per context, and where a context cannot be made to work, the interstitial we use instead and what it costs you in drop-off. Deferred routing, honestly: Deferred deep linking on iOS is a probability, not a fact. The pasteboard route now prompts the user and spends first-launch trust to buy a match. Fingerprint matching degrades with each OS release. We implement deferred routing through your MMP, measure the match rate against a control you can audit, and report it as a rate with its sample size. Where the destination matters more than the friction, a creator's code, a referral, a specific product page, we build a first-launch claim step that does not depend on matching at all. Where this pays back: A pet app whose renewal email lands on the subscription screen instead of the home tab. A beauty launch where a creator's link opens the shade that creator is wearing rather than the catalogue. A crypto app where a referral has to survive a store round trip and land the new user on a funded state, not a generic onboarding carousel. Three routing problems, none of them media problems, all of them usually blamed on media. What we do not do: We do not let paid traffic into a link scheme before it has passed its own test matrix. We do not report deferred deep link success without the match rate underneath it. We do not build a routing layer only we can operate: the contract, the matrix and the monitors go to a named engineer on your side, and if there is no name we do not start. Who this is not for: Apps with no release scheduled. Teams who want a link shortener with a dashboard, which is a feature of the MMP you already pay for. And anyone who wants a deferred match rate stated as a guarantee. We will show you the measured rate from a comparable app and refuse to promise yours.