Your Desktop was the Master Sync. Your phone gets the info from the Master most of the time. So if you wanted to delete, you should have disconnected your phone from Sync. By leaving it on you synced with the Master that had no information so it deleted it all to be the same as it is suppose to.

• https://support.mozilla.org/en-US/kb/how-do-i-set-sync-my-computer
• https://support.mozilla.org/en-US/kb/how-do-i-choose-what-types-information-sync-firefox
• https://support.mozilla.org/en-US/kb/firefox-sync-troubleshooting-and-tips
• https://support.mozilla.org/en-US/kb/view-synced-tabs-other-devices

Profile :

• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data
• https://support.mozilla.org/en-US/kb/recover-lost-or-missing-bookmarks
• https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile

What's What in the Profile :

• bookmarks and history: places.sqlite
• bookmark backups: compressed .jsonlz4 JSON backups in the bookmarkbackups folder

If a jsonlz4 backup can't be imported restored because it has the same structural problem as the database, a user can try to fix it using the Check/Repair JSON button on this page:

• https://www.jeffersonscher.com/res/bookbackreader.html
• formhistory.sqlite for saved autocomplete Form Data
• logins.json (passwords) and key4.db (58+) or key3.db (57 and older) (decryption key) for Passwords saved in the Password Manager
• if you only have key3.db then make sure to remove an existing key4.db

Note : Sync does not replace doing Backups :

• https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles
• https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer

Hi Pkshadow!

When I noticed the problem first thing was disconnect my phone from internet (to save my passwords), than disconnect my desktop Firefox.

Afthe my desktop Firefox was offline, I turned on the internet on my Android Firefox and then start the sync on my Android...and passwords disappeared.

But I don't know what happend, because my bookmarks and sessions are not lost, just the password. And on some pages the user names can be choosen from a list. There is the old user names but the passwords didn't saved anymore.

Do you have any idea to solve this? I don't have backup from my Firefox.

Hi wiki003, if you don't make backups, one possible source of an old version of the relevant files is a Windows Restore Point. Usually these are created when Windows 10 does its monthly updates.

Do not use Windows System Restore!! That typically makes things worse. But you can use a utility program to search inside shadow copies of your user data to try to locate an old file. Here are the steps:

(1) Set Windows to show hidden files and folders:

https://support.microsoft.com/en-us/help/14201/windows-show-hidden-files

(2) Download and run one of these programs:

• ShadowExplorer: http://www.shadowexplorer.com/
• System Restore Explorer: http://nicbedford.co.uk/software/systemrestoreexplorer/

Within the most recent restore point shown in the program, you can explore along this path to see whether you can find a recent shadow copy of your profile:

\Users\your-user-name\AppData\Roaming\Mozilla\Firefox\Profiles\

(3) Export a recent copy of this set of files to a convenient location such as your currently live desktop. Then you can try to swap them into your currently active profile in place of what's there to see whether that brings back your passwords.

• logins.json
• key4.db
• key3.db

Firefox switched to key4.db at some point, so if key3.db is gone, don't worry about it.

If you found some candidate files to try...

(1) From inside Firefox, open your current Firefox settings (AKA Firefox profile) folder using either

• "3-bar" menu button > "?" Help > Troubleshooting Information
• (menu bar) Help > Troubleshooting Information
• type or paste about:support in the address bar and press Enter

In the first table on the page, click the "Open Folder" button. This should launch a Windows Explorer window listing the various files and folders in your profile.

(2) Leaving that window open, switch back to Firefox and Exit, either:

• "3-bar" menu button > "power" button Exit
• (menu bar) File > Exit

Pause while Firefox finishes its cleanup, then:

• right-click > Rename logins.json to loginsOLD.json
• right-click > Rename key4.db to key4OLD.db

(3) Then copy/paste into the folder the files you extracted from the restore point.

When you start Firefox, it should use those older files. Success?

Thank you jscher2000!

The recommanded programs didn't find any restore points. :O But system restore is active on my Windows.

Now, I added my passwords which I remember. If some of them are lost, maybe they were not important.