How to Check if a Browser Has Installed Protocol Handlers for Custom URLs?

Detecting Browser's Protocol Handlers

To handle situations where a custom URL protocol handler is not installed for a browser, it's crucial to identify the registered protocol handlers within the browser. While searching for a solution, a novel technique was uncovered that leverages JavaScript's event-handling capabilities.

Detecting Protocol Handler Existence

This method involves attaching an event handler to the desired link that sets a timer and adds an additional event handler for the window's onblur event. Theoretically, if the browser handles the link, an external application should load and take focus away from the window. If the onblur event never fires, it indicates that the window still has focus, suggesting the link was not properly handled by the browser. A timeout is set for 3-5 seconds to give ample time for the external application to load and take focus. If the timeout expires, it implies that the necessary protocol handler is not installed.

Notification to User

When the timeout triggers, a user-friendly message can be displayed, informing them that the required application is not found and offering them the option to install it.

Limitations

It's important to note that this approach is not entirely foolproof. However, it offers a practical solution to gracefully handle situations where custom protocol handlers are not available. This technique can be particularly useful for applications that heavily rely on custom protocol handlers for seamless user experiences.

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