The extension rewrites the URL to http://«ip»/«hostname»/, and I assume some internal magic to remove the hostname from the path again and to set the correct Host: header.

The problem with this approach is that it breaks some sites; href="/foo", src="/assets/bla.css" removes the /hostname part from the URL, causing these kind of links to break.

I would be interested in a version of this that does not rewrite the URL, but I can imagine that will be hard to do within Firefox' extension API.

The extension seems to just rewrite the URL to replace the domain name with an IP address before making a request. When I add a rule to point www.example.com at 127.0.0.1, and type https://www.example.com in the address bar, the browser just goes to https://127.0.0.1, instead of what I'd expect it to do which was direct the browser to connect to 127.0.0.1 but keep the Host header as www.example.com. It might be useful for people testing non-HTTPS sites without a virtual hosting configuration, but I'm not in that situation so this extension doesn't help with my needs at all.

Pop-up to add new rules is really crappy, closes all the time, does not have a way to update in bulk... and tweaking more settings is required to make it work.

Doesn't set the Host header, but otherwise it works.

Doing a server migration and attempting to test the new server before updating the DNS. I was hoping this would work (I'm using the latest Waterfox 56) though even after properly setting the IP, domain and even restarting the browser outright my website which shows the server IP address in Administrator mode was still pulling the old IP address. Maybe I missed something? Will try another extension. If the author replies with something useful I'd be willing to try again.