User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:57.0) Gecko/20100101 Firefox/57.0 Build ID: 20171112125346 Steps to reproduce: 1. Enable Account syncronization. Set synchronize settings checkbox. 2. Change default gui settings. 3. Add sites to history cookies exception list 4. Change settings in about:config 5. Try to sync this values on this or another pc with clear firefox installation. Actual results: Gui settings not synchronized at all, History cookies exception list is empty not synchronized at all, Settings in about:config are in default state, not synchronized at all. Possibly privacy sites exception list is not synchronized(not tested) Expected results: Firefox must synchronize all settings, not partially.

This is a known issue, sadly; we only sync a small, mostly arbitrary subset of preferences. In the meantime, you can add new ones (or see the ones we sync by default) by setting a Boolean pref for "services.sync.prefs.sync.{pref-name}" in about:config. Bug 1269548 tracks making this better.