Firefox: No connection to localhost domains when offline

After upgrading from Ubuntu 14.04 to Ubuntu 16.04, I was not able to connect to domains pointing to when I had no network connection - in Firefox. In Chrome, it worked correctly.

As a web developer, I have a bunch of projects running on my laptop with domain names defined in /etc/hosts that point to the local machine, On the train I have no internet connection but still want to work on my projects, so it's crucial to be able to access them.


When accessing http://www.bogo/ that has an entry in /etc/hosts, Firefox showed an error page:

Seite wurde nicht gefunden

Die Verbindung mit dem Server schlug fehl.
Falls die Adresse korrekt ist, können Sie noch Folgendes versuchen:

  • Die Seite später noch einmal aufrufen.
  • Die Netzwerkverbindung überprüfen.
  • Falls der Computer sich hinter einer Firewall befindet, überprüfen Sie bitte, ob Firefox der Internetzugriff erlaubt wurde.

In english:

Hmm. We’re having trouble finding that site.

We can’t connect to the server at
If that address is correct, here are three other things you can try:

  • Try again later.
  • Check your network connection.
  • If you are connected but behind a firewall, check that Firefox has permission to access the Web.


I found question that had the correct solution for me:

  1. Open about:config
  2. Search for network.dns.disableIPv6
  3. Set it to false

After that it worked for me.

Firefox bug 1267257 seems to be describing this issue.

Written by Christian Weiske.

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