A guide to setting up Firefox to ensure it is filtering the search terms you set in Guardian.
I have set up some search terms to be blocked, and this works fine with Google Chrome and Internet Explorer browsers. The search terms are not blocked in Firefox, and do not show in the search term logs. Why is this?
Firefox is different from other browsers in two main aspects:
Firefox has its own certificate store
If you are using an HTTPS inspection certificate this needs to be installed in Firefox manually. Go to Options > advanced > Certificates > View Certificates > Authorities tab > Import
This would explain why Yahoo searches were not showing in the Web filter logs as yahoo.com is only available via HTTPS.
bing.com however works via HTTP by default unless you specifically enter https://www.bing.com in the address bar or have an add-on that automatically redirects HTTP requests for known sites to HTTPS, such as HTTPS Everywhere.
Firefox has its own proxy settings
This means that if you are setting your proxy settings in the Internet Options on a Windows device, Chrome, Edge and Internet Explorer will pick this up.
Firefox however has different settings, that can be found under: Options > advanced > Network tab > Configure how Firefox connects to the Internet. To have Firefox pick up the settings you specify them in the operating system. Set it to Use system proxy settings.