https://www.mozilla.org/en-US/firefox/55.0beta/releasenotes/ "Breaking profile changes - do not downgrade Firefox and use a profile that has been opened with Firefox 55+." This specific planed new change has ME WORRIED, so I thought I would start a new question for it.. I already Googled it, and noting relevant except for the beta release notes above came up... What E.X.A.C.T. change(s) are planed or gonna happen.. 1) new file types? ie. replacing the sql-lite db files? etc or.. idk something else? I of course backup my whole profile folder starting from the Mozilla folder in AppData/Roaming... often, at least 2-4 times a month... and I also make one permanent backup of the last snapshot of my FF profile before upgrading to a new major version in case a DOWNGRADE is needed! or a file becomes corrupt like with CCleaner v5.31.6104 messed up part of my profile on June 13th 2017.... which is all better now... so Developers can you provide more details to me and everyone else here on what this vague change(s) entail?