Had a look at my Pi Hole blocked queries list and there are entries for: incoming.telemetry.mozilla.org I thought I had disabled all the 'phone home' functionality in Firefox, but it appears to be still sending telemetry. about:telemetry claims it is disabled but there are several telemetry settings set to true in about:config. I don't know how to turn these off in settings, the only option seems to be to set: toolkit.telemetry.server to an empty address. #Firefox