Navigator: registerProtocolHandler() method

{{APIRef("HTML DOM")}}{{securecontext_header}}

The {{domxref("Navigator")}} method registerProtocolHandler() lets websites register their ability to open or handle particular URL schemes (also known as protocols).

For example, this API lets webmail sites open mailto: URLs, or VoIP sites open tel: URLs.

To register a protocol handler, a website calls registerProtocolHandler(), passing in the protocol to register and a template URL.

When the user activates a link that uses the registered protocol, the browser will insert the href from the activated link into the URL template supplied during handler registration, and navigate the current page to the resulting URL.

The browser may ask the user to confirm that they want the page to be allowed to handle the protocol, either when the protocol is registered or when the user activates the link.

Syntax

registerProtocolHandler(scheme, url)

Parameters

• scheme

  • : A string containing the scheme for the protocol that the site wishes to handle.

    This may be a custom scheme, in which case the scheme's name:

    • Begins with web+
    • Contains at least one letter after the web+ prefix
    • Contains only lowercase {{Glossary("ASCII")}} letters.

    Otherwise, the scheme must be one of the following:

    • bitcoin
    • ftp
    • ftps
    • geo
    • im
    • irc
    • ircs
    • magnet
    • mailto
    • matrix
    • mms
    • news
    • nntp
    • openpgp4fpr
    • sftp
    • sip
    • sms
    • smsto
    • ssh
    • tel
    • urn
    • webcal
    • wtai
    • xmpp
    <!-- This must match: https://html.spec.whatwg.org/multipage/system-state.html#safelisted-scheme -->

• url

  • : A string containing the URL of the handler. This URL must include %s, as a placeholder that will be replaced with the escaped URL to be handled.

    The handler URL must use the https scheme, and must be of the same {{glossary("origin")}} as the webpage that is attempting to register the handler.

Return value

None ({{jsxref("undefined")}}).

Exceptions

• SecurityError {{domxref("DOMException")}}

  • : The user agent blocked the registration. This might happen if:
    • The registered scheme (protocol) is invalid, such as a scheme the browser handles itself (https:, about:, etc.)
    • The handler URL's {{Glossary("origin")}} does not match the origin of the page calling this API.
    • The handler's URL's scheme is not https.

• SyntaxError {{domxref("DOMException")}}

  • : The %s placeholder is missing from the handler URL.

Examples

Registering a handler for the mailto protocol

It's fairly common for web pages to link to resources using non-https protocols. An example is the mailto: protocol. Web authors can use a mailto link when they want to provide a convenient way for users to send an email directly from the webpage:

<a href="mailto:[email protected]">Web Master</a>

When the link is activated, the browser should launch the default desktop application for handling email. You can think of this as a desktop-based protocol handler.

Web-based protocol handlers allow web-based applications to participate in the process too. An email web app at mail.example.org can register to handle mailto links with code like this:

navigator.registerProtocolHandler("mailto", "https://mail.example.org/?to=%s");

After this, when the user clicks a mailto link on any website, the browser will (after possibly asking the browser for confirmation) navigate to https://mail.example.org/?to=mailto:[email protected]. This page could parse the URL parameter to extract the address, and use this to initialize an email.

Registering a handler for a custom protocol

In this example, a page registers a handler for the web+burger protocol with code like this:

navigator.registerProtocolHandler(
  "web+burger",
  "https://burgers.example.org/?burger=%s",
);

Subsequently, the user visit a page containing a link like this:

<a href="web+burger:cheeseburger">cheeseburger</a>

If the user activates the web+burger link, the browser will (after possibly asking the user for confirmation) navigate to https://burgers.example.org/?burger=web+burger:cheeseburger.

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}