"App deep linking" via meta tags lets a site declare a companion native app, enabling platform-specific UX where the OS offers to open the page in the app instead of the browser.
iOS Safari smart banner -- triggered by:
<meta name="apple-itunes-app" content="app-id=123456789, app-argument=https://example.com/article/42">
When the user visits the page in Safari on iOS, an unobtrusive banner appears at the top with the app icon, title, and an "Open" button. The app-argument lets you pass a deep-link URL the app can use to navigate to the equivalent in-app content.
Android Chrome -- triggered by:
<meta name="google-play-app" content="app-id=com.example.app">
<link rel="alternate" href="android-app://com.example.app/https/example.com/article/42">
Combined with Android App Links (a manifest entry on the app side that claims specific HTTPS URLs), Chrome on Android can offer to open the page in the app. The <link rel="alternate" href="android-app://"> is the more flexible mechanism for per-page deep links.
When to use:
- You have a published companion app (App Store / Play Store).
- The app provides genuinely different / better functionality than the web version (offline support, push notifications, native integrations).
- Your users actually use the app -- the banner is annoying friction when most users just want the web version.
When NOT to use:
- The app is a thin web wrapper -- users get nothing extra from switching.
- You're using the banner as a "download our app" advertisement -- iOS specifically allows users to dismiss the banner, but it still costs trust if it's perceived as nagging.
Modern alternative: PWA install prompt -- if your site is a real PWA (manifest + service worker + HTTPS), Chrome and Edge offer to install it as an installable web app, often with better UX than a native-app smart banner because there's no App Store roundtrip.