Firefox Windows "Vanish" & Re-appear on Restart
This is a continuation of the problem report (with the exact same question) that had no solutions and was recently closed. I have no idea why an active problem report was closed.
I had the same problem last night. After a BSOD Firefox started (I start it automatically via the startup menu). Only 9 of my 10 Firefox windows were started; the main window I use was not started. Note that I ALWAYS run Firefox with add-ons disabled. I took a dump of the firefox.exe application via the task manager. Then I clicked on "Help - Restart with Add-ons Disabled...", and Firefox re-started with all my 10 windows. How do we diagnose what is happening? Is there anything in the dump that might help in resolving this? If not, is there any other diagnostic tool that we can use to figure out what is happening? This does not happen with every start/restart of Firefox, but it happens often enough to want me (a computer professional) to find a solution. Thanks.
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HI Barry, Thank you for your question. I understand that when you restart Firefox in Safe Mode (as you do always) that there is one window missing when your session restores.
There are a few work arounds I can suggest:
- When this happens, see if you can restore the previous session from History> Restore Previous Session
- Since extensions are not turned off in Safe Mode, you can also check to see if its an extension: Please update your plugins to the latest version. Check to make sure you are up to date:
If you see any issues also see:
- Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems
- Do the windows have more than 50 entries, there is a limit in browser.sessionhistory.max_entries that can be changed if there are more.
- IF there is important info missing you can also check the files that Firefox stores sessionbackups in: https://support.mozilla.org/en-US/questions/1027904
I hope this helps.
I am getting confused about add-ons vs. plug-ins. I keep my Adobe flash up-to-date via
That URL told me that I have 126.96.36.199 installed. But the plug-in manager claimed that I have 188.8.131.527 installed. I followed the directions, and I supposedly updated the Adobe flash. Firefox automatically restarted, but it restarted in regular mode. I had to re-start it in safe mode. After that restart, the plug-ins page still claims that my installed 184.108.40.2067 is out-of-date. That plug-ins page says that my Adobe Acrobat Reader plug-in is out-of-date, but I did not try to update it.
When I restart Firefox (and I do it about twice a week due to large private storage usage), SOMETIMES not all of the windows appear. Sometimes it is what I call my "main" window, but I am not sure if that window is listed first in the internal list of open windows. I no longer have a sessstore.js file to see the ordering of the windows. Sometimes it is a different window that does not appear. And most of the time, all of the windows start properly. This is an intermittent problem, and I have not found a pattern.
What does "History - Restore previous session" do? From where does it get its data? I do see a sessstore-backups\previous.js and recovery.js files. These must have been relatively new changes to Firefox, as I used to use/process the sessionstore.js and sessstore.bak files. I have awk scripts to process these two sessstore files.
I had another occurrence a few minutes ago. My machine experienced a BSOD at 2:44 this morning, and it rebooted. When I got to the machine at 8:10 and entered my password, Firefox started, but without my main window. I took a dump via the task manager. Then I went to "history", and "Restore previous session" was grey and NOT available as an option.
Barry that is correct, in version 33 the session back up folder was added and the session management was redesigned. The new one acts similarly.
best thing to recover from a session loss like that would be to quit Firefox and then backup all files matching $profile/sessionstore*. So you can't lose anything when trying different approaches. Copy /sessionstore-backups/FILE to /sessionstore.js in the following order where FILE=...
1) recovery.js 2) recovery.bak 3) upgrade.js-XXX
One of those should work and have at least most of the lost data. After copying you can start Firefox and see if that worked. If it didn't then quit Firefox and try the next FILE.
However this is for general restore between new profiles, and Firefox installations. So the fact that one window is missing as such could just be the timing of how often the backups are overwritten. (maybe 5mins or something similar, you can find it in the about:config session back up configurations)
When this has been greyed out there might be something wrong with one of the files afaik.
The BSOD I do not know exactly what can cause this, but for recovery you can look for those files listed above for a manual restore.
Thanks for the information on the three restore files. I may look at these for diagnostic purposes. in my case, when the window vanishes, it re-appears when I restart Firefox via Help-restart without add-ons. I have to assume that each of the three session store restore files will have the missing window. When I restart Firefox via the help menu, is any of these session store restore files used? Or is the current configuration used? For example, does Firefox save the current session in recovery.js, shutdown, and then use the recovery.js file to restart?
In any case, this does not help in determining why the window vanishes, as Firefox still knows about it upon restart.
Here is more information on the problem. Yesterday I started a new window because I was starting a new project, and I wanted the tabs for that project in its own window. The total is now 12 windows. I rebooted this morning after installing Microsoft Windows 7 patches. This afternoon I noticed that the new window was not in the Firefox list of windows; I had viewed that window after the 09:02 reboot. When I saw that the window had vanished, I revised my sessstore scripts to use the new sessstore-backups directory. In that directory I had three relevant files:
previous.js 07/08/2015 09:00 recovery.bak 07/08/2015 15:12 recovery.js 07/08/2015 15:13
I ran my copy and awk scripts against each of these three files, and each of the files had 11 windows. The vanished window did NOT appear in these files. I then did my usual "help-restart with add-ons disabled", and the resulting restart gave me back my vanished window. This is very confusing.
So in Safe Mode all of the windows restore correctly. It has to be an add on. If you have already tried to disable each one by one I can only guess there might be malware.
I am ALWAYS running in safe mode. I was in safe mode when the window vanished. The only time I run not in safe mode is when FF starts and for some unknown reason the SHIFT key depression is not recognized. When this happens, I wait until FF is responding, and then I restart in safe mode.
The problem has recurred today. After a BSOD reboot, Firefox showed 12 windows; one was missing. I copied the restore files, and I processed them with my awk script to make them readable.
previous,js 150804 15:14 11 windows (2 missing) recovery.bak 150806 14:21 13 windows recovery.js 150806 14:22 13 windows
NOTE that all of this is in safe mode. I did a Help-restart in safe mode, and Firefox showed only 10 windows. After processing the restore files, I see
previous,js 150804 15:18 13 windows recovery.bak 150806 15:20 13 windows recovery.js 150806 15:21 13 windows
Nothing is missing in these three files, but Firefox does not show me three windows; they have "vanished".
I am about to restart Firefox again to see how many windows it shows.
previous,js 150804 15:18 13 windows
Should be 150806.
An update: I did an exit and a start in safe mode. Firefox showed 10 windows. Then I closed two windows, each of which had one tab - a graphical image. Then I did the usual "Help - restart in safe mode", and Windows showed 8 windows. I processed the three restore files, and I see
previous,js 150806 15:49 11 windows recovery.bak 150806 15:51 11 windows recovery.js 150806 15:52 11 windows
These three files have all of my windows. But the one window I need for a current project is not being shown. Is there any way I can get that window to display?
I am running 39.0 and I see that 39.0.3 is available, I will update now and then report the results.
An update. After I installed 39.0.3, Firefox started with all 11 windows. Now I have the window I need right now. But the question I still have is this - when I get into this situation again (and I assume that the 39.0.3 update did not fix this problem), how do I get diagnostic information to help debug this problem? Is there no one else who has experienced this problem? Is there no one else who has 10 or more windows open?
The problem recurred this afternoon. Firefox 40.0.3 running in safe mode crashed; i haVe not yet looked at the error log. I then restarted Firefox (in safe mode), and after a while (of doing other things), I noticed that only 10 of my windows were shown; my "main" window was missing. I capturred the three files - previous.js, recovery.bak, and recovery.js . I have not had a chance to look at those files. I did my usual "help-Restart with add-ons disabled", and Firefox restarted with all of the 11 windows.
The problem recurred again. My computer had a BSOD reboot, and upon restart Firefox had only 10 windows. My "main" window was missing. I then did the usual "Help - Restart with add-ons disabled:. Firefox started, but NOT in safe mode. It had all 11 windows. I then repeated the restart, and Firefox re-started in safe mode with all 11 windows I saved the three backup files, but I have not looked at them. I assume, from previous experience that all three have all of the 11 Firefox windows.
I still have the unanswered questions - 1) WHAT IS HAPPENING? and 2) HOW DO I DEBUG THIS PROBLEM?
I had another occurrance today., Yesterday (9/23) FF crashed at 01:27. Around 23:15 I restarted FF. Then I noticed this morning that only 9 windows were showing; one that I wanted was not there, I captured the three backup files for processing, and I exited FF. I restarted FF, but for some unknown reason it did not see that I was depressing the Shift key, so FF started in regular mode. There were 11 windows. Then I restarted in safe mode, and all 11 windows were present. WHAt IS HAPPENING?
Another update. I installed a MS patch this afternoon (one that was re-issued). After the required reboot, Firefox started with 10 of my 11 windows. I ran my script to process the three files (previous,js, recovery,js, and recovery.bat). Then I exited and restarted Firetox to get the 11th window started. Also, when I depress the SHIFT key and click on the Firefox icon in the system tray (or on my desktop), Firefox does NOT start in safe mode. I have to wait for Firefox to stabilize before I can click on Help-Restart with add-ons disabled.
As I have written before - is there any way I can help debug what is happening when a window does not open? Note that I am running 42.0.
Did you ever check for Recently Closed Tabs/Windows ?
Did you try to start Firefox another time in normal mode in cases where not all windows got restored/
Note that it is best to immediately make a backup of all files in the sessionstore-backups folder when something goes wrong. It could also be that the window opened but wasn't visible for some reason (off screen or collapsed). Alt + Tab could possibly reveal such a hidden window.
I do not check for Recently Closed Tabs/Windows, because I know that I had not closed the window that had vanished. And if I had closed the window, it would not appear when I restarted Firefox. I will have to remember to check this the next time Firefox "vanishes" a window.
When a window has vanished, I restart Firefox, and the window re-appears. I am not sure how I start Firefox. I have set the Firefox that I have in the startup directory so that on reboot, Firefox will start in safe mode. The icon on my desktop does not have the "-safe-mode" association, so when I click on that icon (or the icon in the system tray), Firefox will start in regular mode. When I start Firefox by using the desktop icon, I ensure that I am depressing the SHIFT key. I always want to run in safe mode to ensure that problems I have with Firefox are not caused by add-ons.
I notice the missing window when I move the mouse over the icon in the system tray to find a window to which to switch. When I do not see the window, I look at each window and determine with which "project" the window is associated. I have not tried alt-tab. Next time I will have to try that. I have taped a note to my computer to check this and "recently closed windows" the next time a window vanishes.
I had another occurrence this morning. at 05:00 the system experienced another 116 TDR graphics driver BSOD, and when I got to the computer at 08:00, I re-entered my password (after the reboot). Firefox started with only 10 windows; the main window I use was not there. I checked History - Recently closed windows, and my main window was not there. All I saw were a few tabs I had closed yesterday. I did an alt-tab, and I counted 10 Firefox icons, so the missing window was not there. I then did a "help - restart with add-ons enabled, and Firefox re-started with 11 windows. After Firefox started, I restarted with add-ons disabled, and all 11 windows appeared.
I just had another occurrence. I went to Firefox to do some work in a window for the first time today, and there were only 10 windows; the one on which I wanted to work was missing. I saved (and processed) the three "backup" files,, and I did Help-Resart with add-ons enabled. Firefox then started with 11 windows. Once FIrefox would let me, I did Help-Restart with add-ons disabled, and Firefox had the 11 windows. While Firefox was in the 10-window state, alt-tab showed only 10 windows, and History-Recently closed windows did NOT show the missing window.
When this occurs, what diagnostic tools can I use to debug this problem? Obviously the Mozilla support staff cannot do much diagnosis after I have restarted Firefox to recover the missing window.
Firefox had crashed 11/29 (Sunday) at 21:32, and I had restarted it Monday morning (after I had seen that Firefox had crashed).
I think that there are two configurations at play here. On session restore, max windows is 10. (browser.sessionstore.max_tabs_undo) The other max serialize back. In the past this has been recommended to change if no matter the number 10 11, 12 34, that only 10 are recovered in the session.
Does this also happen in Nightly?
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