Universal link
An ordinary HTTPS address that opens the app if installed and the web page otherwise — without the user noticing the difference.
The difference from deep links using a custom URI scheme is verification. The developer places a file on the domain — apple-app-site-association for iOS, assetlinks.json for Android — listing which apps may open which paths. The operating system fetches the file at install time and checks it.
That solves the hijacking problem: another app cannot claim to own your domain. And because the address is a real web URL it works everywhere, including where the app is absent. The price is that setup requires access to the domain and correct server configuration — an incorrect Content-Type is enough to silently break it.