custom protocol handler to launch IE - inconsistent results

Creating a custom protocol handler to launch Internet Explorer (IE) or any other application from a web link can sometimes be inconsistent due to browser behavior, security settings, and operating system differences. Here are a few steps to troubleshoot and ensure consistent behavior:

1. Registry Configuration:
   Make sure the registry configuration for your custom protocol handler is correctly set up. The registry keys should be in the appropriate location and should point to the correct application executable. Check that the keys are correctly set under HKEY_CLASSES_ROOT and that the URL Protocol key is defined.

2. Browser Behavior:
   Different browsers may handle custom protocol handlers differently. Internet Explorer, for example, might have different behavior compared to other browsers like Chrome or Firefox. Test your custom protocol handler with multiple browsers to see if the behavior is consistent.

3. Security Settings:
   Browsers often have security settings that may restrict the handling of custom protocols, especially if they are considered unsafe. Check the browser's settings and security policies to ensure that it's allowing your custom protocol handler to run.

4. File Associations:
   Sometimes, issues with launching applications from custom protocol handlers can be related to file associations. Ensure that the application you're trying to launch (e.g., IE) is properly associated with URLs or web links.

5. Command Line Arguments:
   If you're passing command line arguments to the application you're trying to launch (such as a URL), make sure they're being passed correctly. Some applications might require specific formatting or escaping of characters.

6. Testing on Different Systems:
   Test your custom protocol handler on different systems (different versions of Windows, different browsers) to see if the inconsistent behavior is specific to a particular environment.

7. Debugging and Logging:
   Add logging statements to your custom protocol handler code to see what's happening when the handler is invoked. This can help you identify any errors or unexpected behavior.

8. Clear Cache and Cookies:
   Sometimes, browser caches or cookies can interfere with the behavior of custom protocol handlers. Clear the browser's cache and cookies and try again.

9. Use HTTPS Links:
   In some cases, using HTTPS links might have more consistent behavior compared to HTTP links, as some browsers and security settings may treat HTTPS links differently.

10. Fallback Mechanism:
    Consider implementing a fallback mechanism in your application. For example, if the custom protocol handler fails to launch the desired application, you could provide a link or a message for the user to manually open the link in a browser.

11. External Protocol Handlers:
    There are third-party tools and libraries available that can help manage custom protocol handlers more easily. These tools might provide more consistent behavior across different systems and browsers.

Remember that working with custom protocol handlers involves interactions between the operating system, the browser, and the application being launched. Inconsistencies can arise from differences in how each component handles these interactions. By thoroughly testing your custom protocol handler in different scenarios and environments, you can identify and address any inconsistencies.