Quickstart: connect your app with an SDK

OptoLink ships four SDKs. Each install page is one path from an empty project to a working link — pick yours and follow it:

Your app is…	Follow	You end with
Flutter (iOS + Android from one codebase)	Flutter: install & initialize	A link tap opening your app on both platforms
Native iOS (Swift)	iOS: install & initialize	A Universal Link opening your app
Native Android (Kotlin)	Android: install & initialize	An App Link opening your app
Node.js 18+ (server, scripts, tooling)	Node: install & initialize	A ten-line script that creates links and QR codes

Not building an app? The REST API reference covers the same surface with any HTTP client.

What every path needs first

1. An OptoLink organization with your app registered. Sign up, then run the onboarding wizard in Set up your organization — step ② is where the app config lives (bundle ID / package name, store URL, signing fingerprints). The mobile SDKs verify against exactly that config, so register it before you fight App Link verification.

2. The right API key tier. Minted on the portal's API keys page:

   Key	Prefix	Works in
   Mobile SDK Integration Key	opl_sdk_…	Flutter, iOS, Android SDKs
   Server API Key	opl_api_…	Node SDK and server-side HTTP clients

   The tiers are enforced by the backend, not by convention: a server key in a mobile SDK, or a mobile key in the Node SDK, fails with 403.

3. An OptoLink backend at v2.1.0 or newer. All four SDKs require it; the deferred-match and telemetry surfaces don't exist on older backends.

Your first win

• Mobile (Flutter / iOS / Android): the install page hands off to a quickstart or testing page — tap a link, see your app open with the resolved path, then reinstall from a click and see the deferred match land. Budget an hour the first time; the platform entitlements (associated domains, App Links), not the SDK, are what take the time.
• Node: the quickstart creates a link, prints its share URL, and fetches a QR code — working end to end in a couple of minutes.