Firefox bookmarks, browsing-session data and the full profile are related but distinct recovery sources. Preserve the profile before replacing files or restoring backups. Bookmark restoration replaces the current bookmark set; session restoration recovers tabs/windows rather than a versioned copy of every page’s content.
Identify and preserve the correct profile
In Firefox desktop, open about:support and use Profile Folder > Open Folder under Application Basics. Record the Firefox version and profile path. Close Firefox completely before copying its profile to a safe recovery location.
The conventional Windows profile root is %APPDATA%\Mozilla\Firefox\Profiles, but Microsoft Store/MSIX installations have a different package path. The actual about:support location is preferable to guessing from a folder name. Mozilla’s profile documentation explains these differences and identifies places.sqlite, bookmarkbackups and session data.
If Firefox will not start, preserve the relevant profile folders before reinstalling or resetting. An Old Firefox Data folder may also contain a previous profile; inspect it as a candidate without overwriting the current profile.
Restore bookmarks from an available backup
Open Bookmarks > Manage bookmarks, then Import and Backup > Restore. Choose a dated automatic backup, or Choose File for a saved backup. Before confirming, preserve the current bookmarks/profile because restoration replaces the current set. For merging bookmarks, HTML import has different behavior from backup restoration.
Mozilla currently documents retention of the last 15 automatic bookmark backups. Inspect which dates actually exist rather than assuming a backup predates the loss. See Restore bookmarks from backup.
Check recovered folders and a few known URLs. Firefox Sync updates changes between devices and is not a true historical backup; preserve a useful other-device copy before synchronizing further changes.
Restore tabs as a separate task
Use menu > History > Restore Previous Session when available. Check Recently Closed Tabs/Windows for smaller losses. Mozilla’s session restoration guide distinguishes normal restart, crash and startup behavior.
Do not repeatedly open and close Firefox before preserving a potentially useful session state. A session contains navigation state; it does not necessarily preserve unsent form content or a complete offline copy of a website. Private windows have different restoration limits. Do not replace internal session files between unmatched Firefox versions without a supported procedure.
If profile files were deleted
Check Recycle Bin, existing backups and the former computer’s user profile. XRecovery can search remaining files on readable storage, exporting candidates to another physical device. Finding places.sqlite or a session filename is a first step. Use Firefox’s matching bookmark or session-recovery workflow on a preserved copy, then check the bookmarks or tabs actually restored.
Validate recovered data in a controlled working profile or supported import route after preserving the original. Check bookmark folders/URLs and the expected windows/tabs separately. Avoid exposing saved passwords, cookies or other private profile contents when handing evidence to someone else.
For the next step, see Document Recovery: Deleted, Unsaved, Overwritten or Damaged?.