Firefox can't access url with name but can with ip address

You can do a DSN Lookup via the tool on the about:networking page to see if at least that works.

See also these prefs on the about:config page.

• browser.fixup.dns_first_for_single_words
• browser.urlbar.dnsResolveSingleWordsAfterSearch [0:never resolve; 1:use heuristics (def); 2:always resolve]

You can open the about:config page via the location/address bar. You can click the button to "Accept the Risk and Continue".

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

Thank you for the reply. The problem is that this worked three days ago. I have not changed the settings. I did not see firefox update itself during that period. So would like to know why it would stop working for machine names on the same network when they can be pinged by machine name, accessed by Edge by machine name and accessed by ip address by firefox. The last two actions suggest it is not a server problem. It also suggests it is not a PC problem. It does seem to be related to firefox. I also have the developer edition of firefox on the PC. That works. Except that was a pretty old version (57) so I upgraded to 84 and it stopped working so I am guessing this is now a built in feature of firefox. Probably best answer is to use Edge for testing.

Actually, this is something different. See:

https://bugzilla.mozilla.org/show_bug.cgi?id=1677806

We're in the process of fixing this remotely. In the mean time, you can flip the pref:

network.dns.dns_query_single_label

to false.

Hi Mike, do I need to restart firefox after the change? Reboot? Tried the change and still same problem. Use http://mint20-loopback4:8080 and server not found. Use 192.168.1.6 and found. With edge both url's work. Ping works from command line of pc.

Just to add downgrading from firefox 83 to firefox 80 does fix the problem. So something was added after 80 to stop being able to use my internal network by name.