When you add the slash at the end, it gets replaced with ".com". It's intended to help you in case you've made a typo, I believe.

It works with every website that I've tested, except for Google domains (YouTube is owned by Google). I assume this is because Google owns "google" as a domain. For example, it has "domains.google". So Firefox detects "http://google" as a valid website. The problem is that Google doesn't appear to have set it up to redirect anywhere, so you don't get a page.

I would assume it's a similar story for YouTube as well.

The only other thing that you've probably noticed is that "riot/" doesn't load "riot.com". That's simply because Riot Games also owns riot.com and just uses it to point to their website. So Firefox loads it, but then is told to redirect to a different website.

What top level domain is added at the end can be changed with the browser.fixup.alternate.suffix preference in the Configuration Editor for Firefox. And if you were interested in turning this feature off, you can set browser.fixup.alternate.enabled to false.

Hope this was the information you are looking for.

Thanks for the response Wesley! I did some additional testing after disabling the `browser.fixup.alternate.enabled` config and it does appear to prevent those from resolving as you mentioned.

One additional point that is still confusing me is that using nslookup to perform DNS queries still resolves these addresses. In this output you can see that my ISP is trying to append a suffix, "attlocal.net", which is failing and then the request for http://riot seems to be succeeding.

``` $ nslookup -debug http://riot Server: 192.168.1.254 Address: 192.168.1.254#53

   QUESTIONS:

http://riot.attlocal.net, type = A, class = IN

   ANSWERS:
   AUTHORITY RECORDS:
   ->  attlocal.net

origin = localhost mail addr = postmaster.localhost serial = 2004052401 refresh = 3600 retry = 1800 expire = 604800 minimum = 3600 ttl = 3600

   ADDITIONAL RECORDS:

• • server can't find http://riot.attlocal.net: NXDOMAIN

Server: 192.168.1.254 Address: 192.168.1.254#53

   QUESTIONS:

http://riot, type = A, class = IN

   ANSWERS:
   ->  http://riot

internet address = 23.217.138.110 ttl = 10

   ->  http://riot

internet address = 23.202.231.169 ttl = 10

   AUTHORITY RECORDS:
   ADDITIONAL RECORDS:

Non-authoritative answer: Name: http://riot Address: 23.217.138.110 Name: http://riot Address: 23.202.231.169 ```

The attlocal.net suffix likely comes from your router. There are various reason that a router may do this. For example, so may do it in case you are trying to access an internal router settings page.

The 192.168.1.254 IP address is likely a local address. The 23.*** addresses listed could be your public IP address or the IP address to some point on your ISPs network.