Web Compatibility Support • Re: Weird behaviour when using websites

If it requires an extension, then it shouldn't register a protocol handler, and the other way around. Seems like the people making that download manager don't know what they are doing? If you're registering a protocol handler in the system then you're telling all browsers to use the designated program; that program should be accessible from any browser. If that program is, in fact, an in-browser extension, then a protocol handler isn't necessary and shouldn't be registered in the system, either.