Did you set the setting as Show my window and tabs from last time in options>General tab . Try in Safe mode if the above not work as normally.

Yep, that's the setting

Tried safe mode, still nothing. Seems that the data of the tabs open has been changed to be just blank tabs somehow.

You can check for problems with the sessionstore.js and sessionstore.bak files in the Firefox profile folder that store session data.

• Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)
• http://kb.mozillazine.org/Profile_folder_-_Firefox
• http://kb.mozillazine.org/Multiple_profile_files_created

Deleting sessionstore.js will cause App Tabs and Tab Groups and open and closed (undo) tabs to get lost and you will have to recreate them (make a note or bookmark them if possible).

Are you using "Clear history when Firefox closes"?

• Tools > Options > Privacy > Firefox will: "Use custom settings for history": [X] "Clear history when Firefox closes" > Settings
• https://support.mozilla.org/kb/remove-recent-browsing-search-and-download-history

If you do then try not to use this feature to see if that has effect.

For Firefox 32 and earlier:

If you haven't already, please back up all your sessionstore files to a safe location for potential salvage operations.

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.

In the window that launches, scroll down and save a copy of all files whose names start with sessionstore 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 blank tabs.

The kinds of files you may find in your new backup of sessionstore files includes:

• sessionstore.js: the windows and tabs in your currently live Firefox session (or, if Firefox is closed, your last session)
• sessionstore.bak: the windows and tabs in your last Firefox session
• sessionstore.bak-datetime: the windows and tabs in the Firefox session that was live at the time of your last update
• sessionstore-1.js (or other numbered files): windows and tabs saved at a time when Firefox was unable to update the sessionstore.js file

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 windows and tabs?

Note that the current Firefox release also keeps backups of sessionstore files in the sessionstore-backups folder in the Firefox profile folder, so you can check out these as well.

You can open a sessionstore file in the Scratchpad (Firefox/Tools > Web Developer). Click the "Pretty Print" button to format the file to see if they still contain the URLs of the pages.

Only thing in the sessionstore files were the tabs of the current and last session, neither being particularly useful. And no, Firefox isn't set to wipe history when it starts.

You could try salvaging tabs you had open at the time of the last update (using the one with the date/time code in the file extension). This post lists different methods for that: https://support.mozilla.org/questions/1021522#answer-633104

993 pages on Word, but at least I have them. Thanks :)

EDIT: Tried the online thingy, will work much better :)