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Deep linking

What are Universal Links?

Short answer

Universal Links are Apple’s https links that open an installed iOS app directly instead of the website, available since iOS 9. They need the Associated Domains entitlement in the app, such as applinks:example.com, and an apple-app-site-association file on the domain. Without the app, the same link simply opens the website.

https://example.com/p/42iOSapple-app-site-associationProduct screenApp installedWebsiteApp not installed
Apple’s CDN delivers the apple-app-site-association file to the iPhone. A tap then opens the app if it’s installed and the website if it isn’t.

How iOS decides

The app lists the domains it handles in its Associated Domains entitlement. The domain publishes an apple-app-site-association file naming the app and the paths it may open. Apple fetches that file through its own CDN rather than straight from your server, so a change can take a while to reach devices.

Why a Universal Link opens Safari instead

Some of it is by design. Typing the URL into Safari’s address bar opens the website, and so does tapping a link to the same domain you’re already on. Many in-app browsers, including those inside social apps, don’t trigger Universal Links at all.

The rest is setup. If the file can’t be fetched or doesn’t list your app, iOS quietly opens the web page. The free Universal Link Validator checks your domain and Apple’s CDN copy of the file side by side.

ExampleAssociated Domains entitlement
applinks:example.com
Read moreComplete Guide to Universal Links for iOS and AndroidHow Universal Links, App Links and deep links work, and how to set them up for your app.

Related terms

  • apple-app-site-association (AASA)

    The apple-app-site-association (AASA) file is a JSON file on your domain that tells iOS which apps may open which links there. It lives at /.well-known/apple-app-site-association, must be served over HTTPS without redirects, and lists each app by its Team ID and bundle ID together with the paths it handles.

  • Android App Links

    Android App Links are https links that Android has verified as belonging to your app, so a tap opens the app directly instead of asking which app to use. They work on Android 6 and later on devices with Google services, and need an intent filter with autoVerify plus an assetlinks.json file on your domain.

  • In-app browser

    An in-app browser is the built-in browser that apps such as Instagram, TikTok, Facebook and LinkedIn use to open links without sending people out of the app. Because it keeps them inside, Universal Links and App Links often don’t open your app from there, and people land on a web page instead.

All glossary terms

One link for every phone

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