What a deep link does
A deep link takes the user to a particular place inside an app, such as a product page, a playlist or a chat with a business. If the app is installed, the phone opens it at that screen. If it is not, a well-built deep link falls back to a web page or the app store listing.
Types of deep links
Modern deep links usually look like ordinary https web addresses that the operating system recognizes as belonging to an app. Apple calls these Universal Links and Android calls them App Links; both require the website owner to publish a small verification file. Older custom URL schemes such as exampleapp://item/42 still work in many apps but fail with an error if the app is missing.
- Universal Links (iOS) and App Links (Android): https URLs verified by the site owner
- Custom URL schemes: app-specific prefixes, no web fallback
- Deferred deep links: send a new user to the store, then to the right screen after install
Using deep links in QR codes
For QR codes, an https deep link is usually the safest choice because it works on every phone, with or without the app. Test the code on both iOS and Android, with the app installed and without it, since the behavior can differ. Many social and messaging platforms publish their own link formats that open their app directly.