Much appreciated! The first looks to be an example of how to register the handler through an installer, instead of the registry hack I'm doing (since MS only wants things actually installed and visible in Add/Remove programs to be protocol handlers, for obvious reasons, even if annoying), and the second isn't barely related, it's looks to be essentially the same thing but in C. Here's mine for comparison: https://github.com/kbenson/urlswitcher-deno