If I reinstall Firefox, will all my data from Firefox Sync come back?

hi, this will only work if you still know your account credentials and don't reset your password in the process.

Sorry, but the Sync service isn't intended for being the only "backup" for your Firefox data. It may work for some users, but they don't come here to report their success. What we see here are the users who can't get it to work and lose all their data with the re-format. I sure as hell wouldn't trust it, and I have "played with" Sync since its inception as the Weave extension, long before it became a standard feature in Firefox 4.0.

At a minimum, backup your Firefox Profile - justin case. https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles Then see if using Sync works for you.

When I have tried it, I found that it works better with the Sync 1.5 version, as opposed to the older (pre-Fx29) Sync 1.0 version. But I was dealing with "throwaway" data in a "test" Profile that I didn't mind losing. An off-shoot of Murphy's Law - if you don't need the data - it won't be lost. But if the data has value - "stuff happens".