We are trying to set up a central autoconfig.js file on a server by Firefox doesn't seem to load the file. I've read https://support.mozilla.org/en-US/kb/customizing-firefox-using-autoconfig and I think I followed the instructions but when trying to add a new site to network.automatic-ntlm-auth.trusted-uris it doesn't get added. I changed the autoconfig.js file in "C:\Program Files (x86)\Mozilla Firefox\defaults\pref" and included the two following lines pref("autoadmin.global_config_url","http://nritcssqlp02/Reports/browse/Custom/mozilla.cfg"); pref("autoadmin.global_config_url.obscure_value", 0); I also tried making mozilla.cfg --> mozilla.js to see if that would work, but it did not. I added NSPR_LOG_FILE and NSPR_LOG_MODULES=MCD:5 as environment variables to try and get some logging to see what was going on. When I open my log file the last line I see is [Main Thread]: D/MCD mcd http request failed with status 191 I tried changing the file from a URL to a location on our file sever and I don't get an error, instead I just get [Main Thread]: D/MCD running MCD url file://nrfsapp/region/donnellyr/FirefoxESR/mozilla.cfg Nothing after that. If I'm reading the documentation correctly, I'm supposed to use the autoconfig.js file on the PC to load the local .cfg file as well as point to where my central file is located. If the central file is different it should over-write the local .cfg file. Is there anything else I can do for testing purposes? Is there something I'm doing wrong here? Thanks.