How to configure Firefox for NTLM SSO (Single-Sign-On)?

• When accessing the relevant site you need to make sure you run Firefox as the Windows user you want to log on as. If you always log onto a workstation as a domain user then there is no issue, otherwise you may need to Shift + right-click the shortcut and choose Run as different user..., or setup a shortcut with your credentials saved
• In Firefox, type about:config In the address bar and press return.
• After the config page loads, in the filter box type: network.automatic. You should see a search result of network.automatic-ntlm-auth.trusted-uris
• Modify network.automatic-ntlm-auth.trusted-uris by double clicking the row and enter the relevent site
• Multiple sites can be added by comma delimiting them such as: https://your_SecureAuth_FQDN.com, https://www.replacewithyourintranetsite.com
• Click OK. You may need to restart Firefox for changes to take effect.

This is based on numerous pages I found on the internet, including this Firefox support page

To authenticate Firefox automatically through a proxy (avoiding NTLM prompt), you have to modify 3 parameters.

• Open the page about:config (in the address bar)

Add your uris (separate with ,) in the following 3 parameters:

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

and change it with the URL of your proxy redirection page, like http://myproxy.local

Modify

• signon.autologin.proxy to be true

If you do it by script, be careful with the dots (.) and the dash (-) in the parameters. This is often the problem.

The suggested solution with network.automatic-ntlm-auth.trusted-uris was not enough in my case. Then I tried the same in network.negotiate-auth.trusted-uris Now it works.