I have a problem with Firefox, which is essentially the same as Firefox redirects localhost to IP.

Whenever I want to access localhost, Firefox wants to connect to an IP (10.26.X.X) which doesn't exist (can't be pinged and has no webserver) and isn't even in my subnet.

Edge and Internet Explorer work just fine, and display my localhost website.

Specifics of my Setup:

  • I have the Firefox Developer Edition 62.0b5 (64-bit).
  • I do not have any extensions installed.
  • Windows 10
  • localhost points to my local IIS Express.
  • This is in a corporate environment, and I have already asked my colleagues who know our network much better than me.

What I have already tried:

  • Flushing the DNS
  • Host file
    • Checking if there is something weird in there
    • Writing 10.26.X.X in the hopes of getting it to use localhost
  • Changing the proxy settings in Firefox and Windows

All this is happening on a new computer, but it was also happening on my old one.

Weirdly it works just fine for my colleague, who gets a 404 Not Found Error (as he does not have an IIS Express Server) instead of a redirect to another IP address.


I have tried connecting to localhost using a normal Firefox (40.0.3) and it redirects to the same IP address.


@Ignacio Vazquez-Abrams I am not sure what you are trying to suggest.

I have tried typing localhost http://localhost/ and https://localhost/.

For https I got an interesting Error message, seemingly from localhost and with branding from my company:

301 Redirect Loop Detected (301_loopback_error)

Your request results in redirection back to

  • Write a bugreport to mozilla; you're using development version. Inform them about this bug! – Ipor Sircer Jul 9 '18 at 10:31
  • Did you try writing "localhost." as the host name? – Ignacio Vazquez-Abrams Jul 9 '18 at 10:51
  • Not full proof by any means, but perhaps try adding a trailing slash e.g. http://localhost/. The slash is often needed with modern Chromium-derived browsers (Chrome, Firefox, Opera) for local addresses. – Anaksunaman Jul 9 '18 at 23:37

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