Hi Chestape, I'm sorry to hear about this problem. Three thoughts:

Could you check whether either of these are available (not hidden or grayed out):

• "3-bar" menu button > Restore Previous Session
• (menu bar) History > Restore Previous Session

If they are missing or grayed, check either:

• "Library" toolbar button > History > Recently Closed Windows (and within each restored window, Recently Closed Tabs)
• (menu bar) History > Recently Closed Windows (and within each restored window, Recently Closed Tabs)

Can you get back any tabs that way?

As an emergency workaround, you could consider installing an add-on that would separately store your open tabs for when Firefox doesn't restore your session. These are the ones I'm aware of that you might investigate/try out:

Use database storage:

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

Use bookmark storage:

• https://addons.mozilla.org/firefox/addon/session-sync/
• https://addons.mozilla.org/firefox/addon/my-sessions/

Another Mac user reported the same problem the other day, so I'm going to link you to that thread:

https://support.mozilla.org/questions/1259936

Ultimately the problem went away after making changes to the Content Blocking settings -- changing from Standard to Custom and choosing some of the new options. I don't see a logical connection, but no reason not to try it. See: Content blocking.

Thank you for your response jscher2000

I can not get my tabs back with the with things you suggested. The restore previous session is grayed out and the recently closed windows and tabs is empty. I read the thread you shared and I did not understand all of it. I looked in my files and could not find a sessionstore. My content blocking is on custom and is only set to block trackers.

Thank you for checking. At this point, I suggest using one of those extensions until we get more information about why this afflicts some Mac users.

I rename Firefox when I install it with the release number so I can always go back to a previous version.

I'm running Firefox66.0.5 with 19 windows and 190 tabs. I downloaded Firefox67.0.0 when it was available, but when I opened it, it didn't restore my previous session, even though all of my upgrades prior to that, including from Firefox.65.whatever to Firefox.66.whatever, always did.

(In fact, when I did open FF67, it had some scary splash screen saying I HAD TO create a Firefox account. Since I don't like being told what to do, and since it hadn't opened up any of my previous tabs and I was afraid if I Quit it it would lose them, I Force Quit it. Holding my breath, I opened Firefox66.0.5 and all my windows and tabs reopened.)

I figured this was just some bug you had and the good folks at Mozilla would fix it, so I waited until Firefox68.0.0 came out. Nope, still doesn't restore all my windows and tabs (but at least no scary splash screen, and an ordinary Quit suffices), so I'll stay on 65.0.5 until you fix the problem.

Hi Steve, are Firefox 67-68 using the same profile as Firefox 66? They may be using a new one with its own data, settings, and add-ons. This article has more info: Dedicated profiles per Firefox installation.

To get an idea of that, you can try this:

Profile Manager Page

Inside Firefox, type or paste about:profiles in the address bar and press Enter/Return to load it.

This page should list at least one profile and could list many. (Each profile has two folders and one or more buttons. Do not use any Remove buttons!)

The profile being used by the Firefox window you are using will have this:

This is the profile in use and it cannot be deleted.

If another version of Firefox is running, the text next to the profile that is using will be slightly different:

This profile is in use in another application and it cannot be deleted.

Actually, it might be easier to jot down the names of the profiles used in the different versions of Firefox from inside the those versions rather than trying to run them simultaneously.

If you lost personal data then it is possible that a new default-release profile folder has been created. See "Determine if Firefox has created a new profile":

• https://support.mozilla.org/en-US/kb/recover-lost-or-missing-bookmarks

You can open the about:profiles page via the location bar to check whether multiple profiles are present and what profile Firefox currently is using.

• Do NOT click any Remove button on this page.
• https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles

Firefox 67 and later can use a dedicated profile for each of the Firefox update channels and will lock the profile, so it can only be used by Firefox in a specific installation folder. For Release versions this profile would be a xxxxxxxx.default-release profile, profiles used in older Firefox versions usually used a xxxxxxxx.default profile (a refresh adds a time stamp).

• https://support.mozilla.org/en-US/kb/dedicated-profiles-firefox-installation

I didn't change any profiles. Did Firefox 67 create a new profile?

Anyway, I have these profiles: default (Created Monday, March 5, 2012 at 5:26 PM. I can't remember what version of Firefox I was using in 2012.) Bug1208342 (Created September 27, 2015 at 8:25 AM by me for debugging that particular bug) CleanProfileForDebugging (Created November 7, 2016 at 12:04 PM by me for debugging yet another problem) default-release (Created Saturday, May 25, 2019 at 8:50 AM; I didn't create this myself, but I did download Firefox 67.0.dmg on May 23rd, so my trying it a few days later would make sense) default-release-1 (Created July 22, 2019 at 11:53 AM; I downloaded Firefox 68.0.dmg on July 15, so again trying it a few days later would make sense)

I'd also post the last modified dates but Get Info reset them all to "Now".

I only run one version of Firefox at a time. I never try running two at once. (It used to say that one version was already running.)

So are you saying (or implying) that FF67 created a new profile, instead of reusing my default profile? Should I just make default-release a symlink (MacOS "alias") to default? And then why does FF68 create yet another profile?

[Pause to read https://support.mozilla.org/en-US/kb/dedicated-profiles-firefox-installation].

Oh, I see, you made things complicated for the average user in order to make things simple for the sophisticated user, perhaps to push Sync (I don't want my data in your cloud, thank you very much).

[Pause to read https://support.mozilla.org/en-US/kb/recover-user-data-missing-after-firefox-update].

That seems to be the explanation. I will try that.

But you know, when you make a new profile for a new version of Firefox, it should contain the instructions for getting back the old profile. One shouldn't have to be put through these hoops.

Of course, I have to print out those articles before I quit Firefox, because when I start the new version it won't have those pages open for me :-(.

Okay, I tried that. It launched a new instance of Firefox (there are now two Firefox67.0.0 icons in my Dock), and the new one has all my windows. But in which instance do I click "Set as default profile"? Or does it not matter?

I think it doesn't matter, but just to be safe, I Quit the instance that had opened all my windows, and in the original instance (the one that was opened to about:profiles) I clicked "Set as default profile". I didn't want to trust "Restart normally..." (since I wasn't sure which FF it would open), so I Quit that instance of Firefox, and when it finished Quitting I relaunched it, and it opened up all my windows and tabs. So that's the answer.

Now to do that with Firefox 68.0.0.

And that works, too. So now I have a new recipe for upgrading, that will work until the Mozillans decide to break that, too.

Also happened to me on V68 with Windows 8.1. I only have one profile. Previous session/windows/tabs all empty on restart. Individual pages were still showing in 'Show all history' but it's a real pain rebuilding a session that way. This wasn't as a result of an update as I've been using the most recent version for at least a couple of weeks.

Phil: When you opened V68, and entered about:profiles in a tab, did it only show one profile? What was the name of the profile?

Also, in about:preferences, do you have "Restore previous session" checked under Startup?

What version were you using before V68, and can you go back to it and open it?

I just have default profile.

Restore previous session is not checked in startup. I manually restore using restore previous session or recently closed windows.

I updated to 68.0.1 on July 19th so i don't think this problem is necessarily related to the update and I don't want to open a previous version in case that screws up my rebuilt session.

Just curious, what is the name of your default profile?

Also, what were you using prior to 68.0.1?

Phil Strictly said

Also happened to me on V68 with Windows 8.1. I only have one profile. Previous session/windows/tabs all empty on restart.

Hi Phil, if you got the tabs back but the URLs are missing, first, please back up all your session files. Then try exiting Firefox, restarting, and restoring again in case it was a one-time glitch.

Back up Session History files

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

(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 > "?" Help > 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 Folder" (or "Show in Finder") button.

If Firefox is closed:

Type or paste the following into the Windows Run dialog or the system search box and press Enter to launch Windows Explorer:

%APPDATA%\Mozilla\Firefox\Profiles

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, double-click into the sessionstore-backups folder. Save all files here to a safe location such as your Documents folder.

(3) What files did you find?

The kinds of files you may find among your sessionstore files are:

• recovery.jsonlz4: 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.baklz4: a backup copy of recovery.jsonlz4
• previous.jsonlz4: the windows and tabs in your last Firefox session
• upgrade.jsonlz4-build_id: the windows and tabs in the Firefox session that was live at the time of your last update
• some old .js files from Firefox 55 or earlier

If you end up needing those, to preview the contents of a file, you can drag and drop it onto this page, then click Scrounge URLs: https://www.jeffersonscher.com/ffu/scrounger.html

That tool is on my site, so please let me know if it doesn't work for you.

You can also check in Windows Explorer if there is a previous version of the sessionstore.jsonlz4 file available.

• right-click: Properties -> Previous Versions
• https://support.microsoft.com/en-us/help/17128/windows-8-file-history

My Restore Previous Session AND the custom Bookmarks Toolbar I created have both disappeared after I shut down Firefox. This is the second or third time this has happened on my new Mac that I am attempting to learn after years on Windows. (I have also used Firefox for years on Windows, without problems.) Very frustrating!

MacBook Pro, iOS Mojave, Firefox 67.0.4