Does the History menu > Restore Previous Session work?

If "Restore Previous Session" is grayed out on the History menu, then either:

(1) Firefox already restored the previous session, or (2) Firefox didn't find the previous session history file at startup

In the case of #1, you could check the history menu for closed tabs in the same window (by default, Firefox remembers up to 10), and/or for other windows that were closed (by default, Firefox remembers up to 3).

In the case of #2, it could be difficult...

Let's back up a few files. Here's how:

(1) To open your profile folder...

If Firefox is still running:

You can open your current Firefox settings (AKA Firefox profile) folder using either

• "3-bar" menu button > "?" button > 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 "Show Folder" button.

If Firefox is closed:

Type or paste the following into the Windows Run dialog or the system search box and press Enter to launch Windows Explorer:

%APPDATA%\Mozilla\Firefox\Profiles

In that folder, do you see a semi-randomly-named folder? If so, click into it. If you find multiple such folders, find the one that was most recently updated.

(2) Copy out session history files

In your profile folder, scroll down and double-click into the sessionstore-backups folder. Save all files here to a safe location, such as your Documents folder. If not too much time has passed, we may be able to use them to recover your lost tabs.

(3) What files did you find?

The kinds of files you may find among your sessionstore files are:

• recovery.js: the windows and tabs in your currently live Firefox session (or, if Firefox crashed at the last shutdown and is still closed, your last session)
• recovery.bak: a backup copy of recovery.js
• previous.js: the windows and tabs in your last Firefox session
• upgrade.js-build_id: the windows and tabs in the Firefox session that was live at the time of your last update

Could you take a look at what you have and the date/time of the various files to see whether you think any of them would have the missing tabs?

Note: By default, Windows hides the .js extension. To ensure that you are looking at the files I mentioned, you may want to turn off that feature. This article has the steps: http://windows.microsoft.com/en-us/windows/show-hide-file-name-extensions

Found 3 upgrade.js, latest from june 9th, size approx 2MB. In Notebook it seems to have references to tabs that disappeared. Is there a way to have Firefox use that file info?

Hi finnjacob, yes, you can try substituting the older file for the current one so that Firefox reads it at startup. There is a particular way to do that...

(1) Assuming Firefox is running: from inside Firefox, open your current Firefox settings (AKA Firefox profile) folder using either

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

Pause while Firefox finishes its cleanup -- these changes should occur:

• recovery.js is moved from the sessionstore-backups folder to the main level of the profile folder and renamed to sessionstore.js
• recovery.bak is deleted from sessionstore-backups

Meanwhile, make sure Windows is showing .js extensions. If you need to turn that on, see http://windows.microsoft.com/en-us/wi.../show-hide-file-name-extensions or http://support.microsoft.com/kb/865219.

(3) Once Firefox has stopped updating things, while viewing the main level of the profile folder, rename sessionstore.js to sessionstore.old. If you find a file named sessionstore.bak, delete it.

(4) Copy in the other file you want to restore, and rename it to sessionstore.js -- after the rename, Windows should show it right next to sessionstore.old in alphabetical order

(5) Start Firefox and it should read the swapped in sessionstore.js and restore whatever was in the substitute file; if you do not have Firefox set to restore your previous windows and tabs automatically, use History > Restore Previous Session

Any luck?

Great! Took me back to the situation of June 9th which brought back most of my tabs. Is there a way to have Firefox do these "backups" at regular (and shorter) intervals? My newest .js was a month and half old.

Grateful for your professional help

There is an add-on named Session Manager that captures session history snapshots to a separate folder and allows restoring them on demand. https://addons.mozilla.org/firefox/addon/session-manager/ (I haven't tried it myself)

If you do regular periodic backups, you could point your backup software at the sessionstore-backups folder. I wouldn't point any tools that try to back up continuously, as that could cause occasional failure to update the file. Also, regarding offsite backup services, bear in mind that these files contain live session cookies so should be treated as sensitive.

Thanks again. Will try. Firefox is normally very stable and reliable. First time i had this problem. Thanks for sound advice.