When Ctrl+Shift+t does not work, are either of these available/successful:

• right-click a tab > Undo Close Tab
• History > Recently Closed Tabs

When you did the full uninstall, do you know whether Firefox's program folder was removed (C:\Program Files (x86)\Mozilla Firefox)? We sometimes recommend renaming that folder (e.g., C:\Program Files (x86)\OldFirefox) and running the installer again (it should redetect your settings) to rule out stray/corrupted files in there.

If you want to try installing Firefox 25.0.1 over your Firefox 26.0 install, there is a link to the installer in this article (visit using Firefox 26 to get the correct link): Install an older version of Firefox.

Neither Undo Close Tab nor Recently Closed Tabs are available or work.

When i did the full uninstall, I removed the Program Files folder, as well as any AppData folders, then ran CCleaner.

I may try installing the older version to see if anything changes, if the information I just gave you rules out any other solutions.

Could you check something: before shutting down Firefox, open your active profile folder and see whether Firefox has been updating sessionstore.js (it should have a recent timestamp).

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

Help > Troubleshooting Information > "Show Folder" button

If it looks current:

Make a copy of sessionstore.js and sessionstore.bak in a safe location, and rename sessionstore.js to sessionstore.txt or some other innocuous name.

Leave this window open to your profile folder when exiting Firefox so you can watch what happens to sessionstore.js. I'm a bit suspicious that something may be clearing it, either after shutdown or at startup.

Do you see anything unusual happening?

If Firefox doesn't appear to be saving session history, could you check these settings:

(1) Shut-down cleanup

In your Privacy settings, "Clear history when Firefox closes" should be unchecked.

orange Firefox button (or Tools menu) > Options > Privacy

(2) Sessionstore preferences

You can review these and see whether any settings are not set to their default values. Those might be having some kind of impact on session history.

(1) In a new tab, type or paste about:config in the address bar and press Enter. Click the button promising to be careful.

(2) In the search box above the list, type or paste browser.sess and pause while the list is filtered

Anything unusual?

(By the way, browser.sessionstore.restore_on_demand corresponds to the setting in the Tab options "Don't load tabs until selected".)

So, when I clicked Show Folder, nothing happened. I made an educated guess that it would be in AppData/Roaming/Mozilla which seems to be right, in which case the last modified date is earlier today. That makes sense to me.

Nothing seems to change that file when Firefox was closed.

Privacy settings and sessionstore preferences both seem to be in line.

Have you shut down and restarted Windows since this problem began? When buttons to launch Windows Explorer start failing, I get suspicious that some of the wiring is not functioning.

So even though Firefox is updating sessionstore.js, your session is still not restored?

To see what was in the sessionstore.txt file at the time you backed it up, you could try the techniques in one of these threads to render the file readable in a Firefox tab:

• Using Firefox's Browser Console (formerly known as Error Console): https://support.mozilla.org/en-US/questions/969046#answer-471950

• Using Firefox developer tool "Scratchpad": http://forums.mozillazine.org/viewtopic.php?f=38&t=622036&start=60&p=12098147#p12098147

• Using a third party website: https://firefox-session-restore.herokuapp.com/

I've shut down multiple times. I think that since it goes beyond just the session storage, I'm going to try moving back to 25. If that works, then I can try updating again from there, if the problem is isolated to 26. Thanks for your help

Does Firefox create a sessionstore.js file in the profile folder when you select the startup setting "Show my windows and tabs from last time"?

• Tools > Options > General > Startup: "When Firefox Starts": "Show my windows and tabs from last time"

You can use this button to go to the Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)

Also make sure that you aren't in Private Browsing mode.

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