Handle protocols in Progressive Web Apps

To create a more engaging experience, Progressive Web Apps can handle multiple protocols. A Uniform Resource Locator (URL) is a string that allows clients to identify a resource on the Web. The first part of a URL is the protocol, such as http or mailto, which lets clients know how to retrieve the resource.

With Protocol Handling, when a PWA is being installed, the PWA can register to handle certain allowed protocols. For example, an email client app can register to handle the mailto protocol, or a geolocation app can register to handle the geo protocol.

Custom protocols can also be handled, if a PWA registers a protocol that starts with the web+ prefix.

To learn more about other existing protocols, see List of URI schemes.

Register protocols to handle

To use Protocol Handling, declare which protocols your app handles. This is done in your web app manifest file, by using the protocol_handlers array member.

Each entry in the protocol_handlers array contains a protocol string and a url string:

    "protocol_handlers": [
            "protocol": "mailto",
            "url": "/newEmail?to=%s"

In the above example, the app is registered to handle the mailto protocol. When the operating system launches the app in response to the mailto protocol, the app navigates to the /newEmail URL, replacing the %s placeholder with the full URL that's being handled.

Test protocols with the DevTools

You can use the Application tool in Microsoft Edge DevTools to verify that Microsoft Edge successfully registered your app as a handler for the protocols you defined in your web app manifest. You can also test protocols and launch your PWA with different URLs and endpoints. For more information, see Test Progressive Web App (PWA) protocol handling.

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