OK, the logins are easy: Just copy the files `key3.db`, `key4.db`, and `logins.json` from the old profile to the new one. Any idea about the history?

places.sqlite = History and Bookmarks.

Note that safest is to use "Help -> About Firefox" to update until you are on the current release, especially if you update from 52 to 78 because there are special so called watershed releases that contain migration code to handle upgrading files to newer schemes (this makes the profile incompatible for downgrading). For the logins (logins.json and key4.db) this is Firefox 72 and running a 52 profile with 78 can cause you to lose logins. In such a case you can run this profile with Firefox 68 ESR to run this migration code.

Note that safest is to use "Help -> About Firefox" to update until you are on the current release, especially if you update from 52 to 78 because there are special so called watershed releases that contain migration code to handle upgrading files to newer schemes (this makes the profile incompatible for downgrading). For the logins (logins.json and key4.db) this is Firefox 72 and running a 52 profile with 78 can cause you to lose logins. In such a case you can run this profile with Firefox 68 ESR to run this migration code.

Upgrading from 52.9 to 78.5 via 68.10 worked in some aspects, but not completely. While the first step, 52.9 to 68.10, worked fine, the second one, 68.10 to 78.5 let the profile in a strange state: I could not open any tabs, which also means: No preferences etc. which open in a new tab.

So far, the copied logins.json and key*.db files seem to work with the new Firefox. Anyway, I'll try with the files, that went through 68.10 just in case.

Thank you!

places.sqlite = History and Bookmarks.

Yes, this works fine, thank you!

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