Hello Since I'm working with a lot of B2B solutions that provide XML or JSON I have used this customer setting in Firefox: network.http.accept.default;text/html;q=0.9,application/xhtml+xml;q=0.8,application/json;q=0.7,application/xml;q=0.6,*/*;q=0.5 In the inspector under teh network tab I see FF is sending this: Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 I'm using FF66.0.2 and this has been working properly before. I can see that the default was changed in release notes, but the documentation still states that one can set this. Why doesn't it work? I've tried this in safe mode as well. No change.