dspjm said

I cannot click the 'my restore previous session' button in 'history'.

When that item is grayed, either:

• Firefox already restored the session. Try using the Closed Windows and Closed Tabs lists on the History menu to restore them.

• Firefox did not find the session history file and therefore cannot restore your previous session. For example, you may have Firefox set to clear history when you close the browser.

Tab Mix Plus used to use a separate form of storage from Firefox's built-in session history files. I haven't looked into it recently. Does Tab Mix Plus seem to have any separate restore feature?

Yes, but it also offers an option to use firefox builtin. I think maybe it's because the session has been restored.

So does it mean that if I don't enable auto restore of sessions, i can still restore session from there?

Sometimes when firefox ask me if I want to restore, I accidentally clicked no. Then I lost all my tabs, which is annoying.

The built-in way to enable automatic restore is through the startup setting here: Startup, home page, tabs, and download settings. I don't know how Tab Mix Plus does it.

So does it mean that if I don't enable auto restore of sessions, i can still restore session from there?

If you have Firefox start with your home page, Restore Previous Session will be available if Firefox saved your session history. So usually yes unless you clear history at shutdown.

Sometimes when firefox ask me if I want to restore, I accidentally clicked no. Then I lost all my tabs, which is annoying.

When does Firefox ask you???

Normally you either get your tabs at startup or you get your home page. Normally Firefox does not ask you at startup whether you want to restore a previous session.

If Firefox crashed and it was not able to restore your session automatically at the next startup, it may show the "this is embarrassing" screen letting you choose which tabs to restore. But you wouldn't expect to see that often unless your Firefox is very troubled.

That's what will happened,the 'this is embarrassing' thing. Since I always shutdown the computer directly without quiting firefox, that should be the problem.

You might have better luck using Exit the next time. Either:

• "3-bar" menu button > "power" button
• (menu bar) File > Quit -- this is a guess

Does Firefox (or Tab Mix Plus) have an easier time restoring your session at the next startup?

Yep, if I quit and start, it will restore the tabs automatically.

Thanks for your great help!

I have the same versions of Ubuntu, Firefox, as the OP, the suggested Tab Mix Plus 0.5.1 options (Crash Recovery and Use Built-in Session Restore) enabled, and the same options enabled in Firefox Preferences as listed in the accepted answer.

My Restore Session tab, which was full previously, shows up as empty today, with nothing I am aware of happening in between. I include a screenshot. I'm really upset. What, if anything, can I do to recover this list of tabs, which was valuable to me?

Hi penthimos, you might be able to get the missing tabs from an old session history file.

First: Do not exit Firefox, or if you closed it, don't re-open it.

If Firefox is still up, check the History menu for "Restore Previous Session" and, if it's not grayed out, try that.

If that is grayed out or doesn't help, 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 "Open Directory" button.

If Firefox is closed:

Find your profile folder on disk in the manner that is done on Linux (?): Profiles - Where Firefox stores your bookmarks, passwords and other user data.

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, outside of any Mozilla directory path (e.g., 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?

Thank you, jscher2000!

The first three types of file are all from this afternoon (and hence too late), but there are three upgrade.js files in the folder from various times in December which look promising!

What should I do now?

You will normally find these files in the sessionstore-backups folder:

previous.js (cleanBackup: copy of sessionstore.js from previous session that was loaded successfully)
recovery.js (latest version of the sessionstore written during runtime)
recovery.bak (previous version of the sessionstore written during runtime)
upgrade.js-<build_id> (backup created during an upgrade of Firefox)

You can copy a file from the sessionstore-backups folder to the main profile and rename the file to sessionstore.js to replace the current file (make a backup copy of the current sessionstore.js).

• upgrade.js-<build_id>, rename to sessionstore.js

See also:

• http://www.ghacks.net/2014/06/27/mozilla-launches-improved-session-restore-firefox-33/

Dear cor-el,

This worked! Thank you!