When this happens, if you check the History menu, is Restore Previous Session available?

• If it's not grayed out, try selecting that to see whether it brings back the session.
• If it's grayed out, either Firefox already tried to restore your session or it did not find a session history file to restore. Does the History menu show any closed windows or tabs?

By the way, if you set Firefox to clear history at shutdown, or if you set Firefox to "Never remember" history, then those will override your startup preference because there won't be a session history file to restore.

Thank you for replying.

Unless I misunderstood you,my History menu does not have "Restore Previous Session" option. FF is not set to clear the History.

When I go to "tools"..."options"...under the title "General" the instruction is "When Firefox starts:Show my windows and tabs from last time".

This used to work until recently.Does not work now.

There are two ways to access the History menu:

• classic menu bar > History
• "3-bar" menu button > History

Both should definitely have an item "Restore Previous Session" among the first three items at the top of the menu.

Yours is completely missing??

Do you use Session Manager, Tab Mix Plus, or any other extension that has a session history feature?

I use the classic menu bar > History I just noticed the "restore previous history" button but it is not an active one,all other buttons are Bold,this one is empty like.

Okay, that faded or grayed text is what you would normally see if Firefox already restored the previous session or if it can't restore.

Were there any Recently Closed Windows on the list?

Before closing Firefox, could you check whether it is recording your actions as you browse? Here's how:

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 new window listing various files and folders in Windows Explorer.

Double-click into the sessionstore-backups folder. If you use the Details view and sort by updated date, you should find that recovery.js was updated within a minute of your last new page load or tab closure (recovery.bak follows not far behind). As you browse, any changes should be made to that file within 15 seconds.

Is Firefox storing your session or is that file missing or out-of-date?

Note: By default, Windows hides the .js extension and some other file extensions. 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 (or in the Windows XP version of Windows Explorer, you can use Tools > Folder Options > View, if I recall correctly).

The last upgrade.js is from 11/10/2014 The recovery.bak is up to date.

I forgot about it,SORRY: Prior to facing this problem Firefox crashed. Don't know if this is the reason for my problem.

If recovery.bak is up-to-date, then recovery.js probably is also up-to-date.

Could you make a backup copy of recovery.js before exiting out of Firefox the next time?

Before exiting Firefox, if you could also check:

Back at the main level of the profile folder, do you see either of these files:

• sessionstore.js
• sessionstore.bak

sessionstore.js normally does NOT exist while Firefox is running, and you can remove (rename or delete) it. sessionstore.bak would be from Firefox 32 or earlier, so you can delete that one if you find it.

I'm a little surprised the upgrade.js is so old. Usually one is created for each Firefox update, so no more than 6 weeks old, often less.

You can start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem.

• Switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance
• Do NOT click the Reset button on the Safe Mode start window

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes