Hmm, it seems to be hidden now and I'm not sure why. Here are two ways to adjust that setting:

Method #1: Unhide the checkbox

This requires a little hack to the page:

(1) Open Firefox's Web Console using Ctrl+Shift+k or using the Developer menu

(2) In the line at the bottom, next to the caret (>>) paste the following script and press Enter to run it

document.getElementById("warnCloseMultiple").removeAttribute("hidden");

(3) Close the web console using the "X" on the far right end of its toolbar

Method #2: Use about:config

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

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

(3) Double-click the browser.tabs.warnOnClose preference to switch it to false if you do not want warnings

Success?

Thanks for your reply jscher2000. Method#2 worked, but setting the browser.tabs.warnOnCloseOtherTabs property to false. Thanks again!

The Tab warn items in "Options/Preferences > General" are hidden when the related prefs have the default value and warnings are enabled. They only show when you toggle the related prefs on the about:config page.

Note that this may require to close and restart Firefox.

• "Warn me when closing multiple tabs" (browser.tabs.warnOnClose: true)
• "Warn me when opening multiple tabs might slow down Firefox" (browser.tabs.warnOnOpen: true)

I tried the changes suggested above with no success. I restarted FF; still opens with one tab. Restarted Windows then opened FF; still opens with one tab.

The "Warn me" options DOES appear, and it is NOT checked. What more can I do? I keep having to select "Restore Closed Windows," then close all the iterations of FF with only one tab and just keep the one with all my tabs.

I DO have "Show my windows and tabs from last time" selected, and it has always worked until today.

I am running Windows 10 Home, Version 1511, OS Build 10586.164 and Firefox 45.0.1.

Hi Julieann01, if I understand correctly:

• You have Firefox set to restore your previous session windows and tabs at startup
• Firefox is loading your session history file as expected, but shows all previous session windows as closed

Hmm, I'm puzzled about this change of behavior.

How do you usually close Firefox? If you have been using the "red X" button, try using the menu instead, either:

• "3-bar" menu button > "power" button
• (menu bar - tap Alt to activate) File > Exit

When you use Exit, none of the windows should be marked as having been closed. On the other hand, using the red X button may cause Windows to send sequential "close Window" commands to Firefox. Normally it all happens so fast that Firefox doesn't update the session history file to show the windows were closed, but possibly something unusual is happening on your Firefox today...

WOW, Mr. Scher, you are really on top of things! I appreciate the immediate response while I'm still here thinking about this issue.

I've always closed FF with the X; I'll try using the menu instead.

I do have Firefox set to restore previous session windows and tabs at startup.

Firefox loads with a single tab. I then have to select "Restore Closed Windows," which causes it to open another iteration of FF with all my tabs, PLUS it also opens all the single-tab windows that I'd previously closed. I never -- normally -- have more than one browser WINDOW open at a time, but I have a BUNCH of tabs that all are things I am trying to keep track of.

OK: I tried using the power button. That worked. Then I tried it again, this time with the X, and it also worked. Maybe it was just being flaky. So the problem may be solved.

Thank you.

OOPS! I guess it was indeed being flaky, because it happened again, and this time there was NO "Restore Closed Windows" option nor anything else. Now I have reopened FF several times because I had things I had to do, but those lost tabs are still lost.

I do still have the "Show synced tabs" page, but . . . is there any way to just have it load all those pages? Otherwise I guess I'll have to select them one at a time and load them? Even that doesn't help me recover the tabs that weren't saved.

How am I going to teach myself to stop using the X to close FF? (Not your problem, but this is killing me!) Even though I have bookmarked pages that I know are important to me, I often open tabs intending to look at them later; if they disappear before I have time to do that, the thought is gone, gone, gone.

Hi Julieann01, Firefox's session history is only short-term memory. You can extend the feature using an add-on -- I haven't tried it myself:

https://addons.mozilla.org/firefox/addon/session-manager/

Now... about the lost tabs... I honestly do not know what Sync will show you, but if those tabs were open for a long time, there might be an extra backup from when Firefox 45.0.1 installed. To check that:

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 to launch a file browsing window.

Scroll down and double-click into the sessionstore-backups folder. Save all files here to a safe location, such as your Documents folder. We may be able to use them to recover your lost tabs.

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

There is a "recovery" file but it's got today's date, so that's no help, but there is one called "previous" that is about 5 days old -- might be good. How do I use it?

PS: I am an experienced computer user (just not so hot with browsers), so I know how most Windows things work (I already had "hide extensions" and all that stuff turned off), so I can probably follow your directions without too much hand-holding. You are great, and I truly appreciate your help in this situation that is beyond me and very frustrating.

At the moment, I am working on my notebook (my desktop is tied up with a long download I don't want to interrupt), and it has all the tabs I want (and then some: I think some may be duplicates)! So, in case "Sync" fails (it's been chancy so far), is there a way I can save the settings from this device and copy/transfer them to my desktop?

Hi Julieann01, when Firefox shuts down properly, it uses recovery.js to create a file named sessionstore.js in the main level of the profile folder (up from sessionstore-backups). To substitute a file, you wait until Firefox has finished shutting down and created sessionstore.js, rename that to, say, sessionstore-old.js, then copy in the file you want to use and rename it to sessionstore.js. When you start Firefox, it should read that file instead of the one it last saved.

All key settings are in the profile folder, so you can make a backup at any time. Copying them over generally mean replacing the existing files, since many are too messy to edit or require special tools. This article describe the contents of the various files: Recovering important data from an old profile.