In many organizations, Internet Explorer is configured to allow NTLM on internal sites, but Firefox is not. To configure Firefox to allow certain sites, follow the steps below:

  1. Open Firefox.
  2. In the address bar, type about:config.
  3. A warning may appear, click the button to continue.

  4. In the Search text box, enter network.automatic.
  5. Double-click the network.automatic-ntlm-auth.trusted-uris entry.
  6. Enter the relevant site address(s).
    Note: Multiple sites can be added by separating them with a comma.
  7. Click OK.
    Note: Firefox may need to be restarted for the changes to take effect.

In some environments, the following three parameters might need to be updated:

  • network.automatic-ntlm-auth.trusted-uris
  • network.negotiate-auth.delegation-uris
  • network.negotiate-auth.trusted-uris

Also, the signon.autologin.proxy may need to be changed to true (double-click the parameter to change the value).