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Firefox Windows "Vanish" & Re-appear on Restart

  • 26 replies
  • 3 have this problem
  • Last reply by John99

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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. This is actually the THIRD instance of this problem report.

I had another4 occurrence a few minutes ago. I installed three MS Windows 7 patches, and a reboot was required. After the reboot, Firefox started with only 10 windows - my main window was missing. I ran my script to archive and process the three files - previous.js, recovery.bat, and recovery.js . Then I exited Firefox and re-started it. On restart, all 11 windows were present. I still do not have an answer to these questions :

1) WHY does this occur?

2) When it does occur, WHAT DIAGNOSTICS can I run to help debug this problem? This is clearly a bug in Firefox, and I want it fixed. I assume that I am the only one who is experiencing this problem, and I am willing to do almost anything to help debug this problem when it next occurs.

For those who have not read the other two problem threads - I am always running the latest non-beta Firefox, and I always run with add-ons disabled. This is a Windows 7 Professional 32-bit system.

--Barry Finkel

All Replies (20)

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I an another occurrence last night. After a BSOD (graphics driver TDR timeout 116 - frequent occurrence, no resolution yet), the machine rebooted. When I logged in, Firefox started with only 10 of my 11 windows. After installing an update to Adobe Acrobat Reader, I had to reboot, and after the reboot Firefox had all 11 windows.

--Barry Finkel

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I had another occurrence this morning. Firefox was running slowly, and using lots of private space. This happens after FF has been running for a few days. I decided to Exit FF and restart it. During the Exit process, FF crashed, and I sent the crash report. When I restarted FF, it only had 10 of my 11 windows. I did an Exit as soon as I could see the window "names" in the system tray icon. Then I restarted FF, and it had all 11 windows. Most of the time when FF starts, I get a screen that tells me that something has happened. I always click on the option to load the previous configuration, and FF loads successfully (but maybe missing a window). As I have asked before - when this problem occurs, WHAT do I need to do to debug the/diagnose the problem? Would a dump via the task manager have any diagnostic information?

--Barry Finkel

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I had another occurrence this afternoon. i am not a good typist, and while typing I depressed an (unknown to me) a sequence of keys that resulted in the start of a shutdown/reboot. When I saw the shutdown pop-up window appear, i immediately clicked CANCEL. I do not know a sequence that would cause a reboot without first asking permission. In any case, by the time I clicked CANCEL, FIrefox had already terminated. When I restarted FF, it came up with only 10 windows. I ran my script to save and process the three FF files, and then i exited FF. i then re-started FF, and it came up with all 11 windows. HOW DO I DEBUG THIS?????

--Barry Finkel

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I just had another occurrence. I was using FF, and my Windows 7 Professional 32-bit displayed a pop-up window - "FIrefox stopped working.; Click to close". I have no idea why FF stopped working. I fond nothing in the EventLog. I started FF in safe mode, and it started with only 11 of my 12 windows. I ran my script to save and process the three FF restart files, and I then Exited FF. When I restarted FF, it started with all of my windows. I STILL HAVE THE SAME QUESTION - WHEN THIS OCCURS, HOW DO I DEBUG IT?????

And another item, which probably should be a different thread/report: Most of the time when FF starts, it gives me a window "Embarrasing" supposedly because something is wrong with my saved configuration files. When this happens, I click "restore", and FF has all of my windows. This morning, after the crash, FF displayed the "Embarrasing" windows, and when I restarted it (after the file capture), it started without that "Embarrasing" page.

--Barry Finkel

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I had another occurrence this morning. Firefox crashed at 7:54, and when I restarted it, it had only 11 of my 12 windows;. WHAT IS HAPPENING? I NEED TO KNOW HOW i CAN DEBUG THIS PROBLEM!!!

I did take a dump via the task manager, and I am about to capture and process the three session store files then restart Firefox

--Barry Finke

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I had another case this morning. FF crashed overnight (a different problem report), and when I restarted it this morning, FF had only 11 of my 12 windows. I took a dump of the firefix.exe process via the task manager. Then I ran my script to save and process the three backup files. Then I did Exit and a start of FF. FF again started with 11 windows. So I again ran my script, did an Exit, and they started FF. This time FF started with a 12 windows.


--Barry Finkel

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Sorry that you got no help yet. I was about to pass by this post because the number of replies looked like you were being helped.

Start Firefox in Safe Mode {web Link} by holding down the <Shift>
key, and then starting Firefox. A small dialog should appear. Click Start In Safe Mode (not Refresh).

Is the problem still there?

While still in Safe Mode,

In the address bar, type about:crashes<enter>. Note: If any reports do not have BP in front of the numbers/letters, click it to submit them.

The crash report is several pages of data. We need the report numbers to see the whole report.

Using your mouse, mark the most resent 7 - 10 crash reports, and copy them. Now go to the reply box below and paste them in.

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Separate Security Issue: Update your Adobe Reader Version 2015.016.20039 Note: Other Software is offered in the download.

Separate Issue; Your System Details shows;

Installed Plug-ins

Shockwave Flash 16.0 r0 Shockwave Flash 20.0 r0 Shockwave Flash 19.0 r0 Shockwave Flash 18.0 r0
Having more than one version of a program may cause issues. You must remove the older programs. Then get the current full installer.

Flash: Grab the uninstaller from here: Uninstall Flash Player | Windows Uninstall Flash Player | Mac

Then reinstall the latest version.

Note: Windows users should download the active_x for Internet Explorer. and the plugin for Plugin-based browsers (like Firefox).

Note: Windows 8 and Windows 10 have built-in flash players and Adobe will cause a conflict. Install the plugin only. Not the active_x.

Flash Player Version: Flash Player (Linux) Version Direct link scans current system and browser Note: Other software is offered in the download. Step 1: Select Operating System Step 2: Select A Version (Firefox, Win IE . . . .) Note: Other software is offered in the download.

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First - My Adobe Acrobat Reader is at 15.016/.20045 . I do not use the FF-supplied reader, as it had problems in the past displaying PDF files. I have told FF to always use Acrobat Reader DC to open PDF files. FF tells me that my Reader plug-in is up-to-date.

Next, you should know from my other problem reports that I ALWAYS start FF in safe mode. If, for some reason, it does not start in safe mode, I switch to safe mode as soon as FF will allow me to access the Help menu,

Why do you want to see crash information? This problem is NOT associated with any crashes, I believe. I have to start FF frequently after crashes, but sometimes I have to start FF after a reboot. I have not kept track of why I started FF when it does not start with all of its windows. This morning, st started without one window after a crash. Then, the restart was also missing a window; the next restart had all my windows. A window was missing after a crash-related restart; then the same window was missing after a clean Exit restart. So, FF still knows about the missing window, because the window will re-appear on some subsequent restart of FF.

--Barry Finkel

If I were to show you the recent dumps, you probably would tell me to stop Dropbox, as DropboxED.34.dll in implicated in some of the dumps. I have not yet replied to my "frequent crashes" problem because I am still awaiting a response from Dropbox support.

What I really need concerning this missing window problem is a way of debugging/diagnosing the problem when it occurs. It usually occurs at a time when I need the missing window, so at that time my primary issue is getting a FF with the missing window. But I will do anything to debug the problem the next time it occurs. I have no idea if the dump I took this morning via the Task Manager will have anything.

When I look at the three files - recovery.js, recovery.bak, and restore.js - all three appear intact and have the missing window.

--Barry Finkel

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About the multiple editions of Flash installed - I have the latest Flash installed. I try to check once a day, as Adobe issues frequent updates. I have installed. One problem with the Flash install process is that it leaves old files around in the \Windows\system32\Macromed\Flash directory. After a patch install, I go to that directory and rename the old .exe, .dll, .ocx, and .ActiveX files. I have no idea if these old files are used by the newer version of flash or by FF, and I have no idea why the flash install process does not remove them.

--Barry Finkel

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FredMcD said

Flash: Grab the uninstaller from here: Uninstall Flash Player | Windows Uninstall Flash Player | Mac
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I thought a bit of cross linking may help here.

Your other threads include the following (With my comments)

  • Current, Fx47. (Possibly related)
    "Firefox becomes non-responsive, 40% CPU, 1.6 Gb private, then crashes"
    1. Current (I will close) Fx45
      "FIrefox Hangs on Start - No I/O /questions/1124771"
    2. Fx32, Sept 2014.
      "Firefox using much CPU; how to find the offending tab/URL?" /questions/1020162
      (Multiple & duplicated plugins apparently installed. Fx Crashing OOM)
  • Duplicates of this
    1. Fx38, June 2015 /questions/1067958
      (From helpdesk comment /questions/1067958#answer-813831 I wonder if part of the issue may be attempts to use back for more than the number configured ?)
    2. Fx34, Dec 2014 /questions/1037358
      (Similar to above, but includes mention of OOM Fx crashes and repeated BSODs .
      Maybe the OS is not stable ? )
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I had another case this evening. FF was misbehaving, as usual, at firefox.exe+253b. I did an Exit, and FF crashed on termination. Then I restarted FF, and only 11 windows were there; my main window was missing.. I did an Exit, and the restart had 11 windows; the Citrix window was missing. An Exit and restart again produced a missing Citrix window. Another Exit and restart produced a FF with all my 12 windows.

--Barry Finkel

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I suggested in another thread you try a new profile, that may well solve such issues.

if you use an new additional profile you may then try to keep projects in their own profile and use multiple profiles.

It may be possible to turn the clock back so to speak and use an older backup of your restore files, but I suspect they may just be getting too big and complex.

If you do try restoring older backups it would be prudent to do so in another profile.

If you do work with Firefox profiles I suggest using suggested default locations, and not to use the delete or rename features of the profile manager, because it is all too easy to lose information until you understand the finer points of the system.

I am not sure if or where we document the sessionstore files but have a look at this blog

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I need to review your suggestions to determine what my next step is. I realized last night that I was capturing and processing in the sessionstore-backups directory these files:


In each case where I had looked at the files reformatted by an awk script, all of my windows were present. I remembered last night that a clean Exit of Firefox places a file


in the parent directory, and it is this file that is used when Firefox starts. I did capture that file before my good 12-window restart last night, and this morning I wrote a script to save and process that file. When I looked at the output of my awk script this morning, I see only FIVE windows present in that file. This seems strange to me, as I thought that the sessionstore.js file was the one used at startup.

When Firefox starts with a missing window, I run my script to capture the three files BEFORE I Exit Firefox. Now I will run my new script to capture the sessionstore.js file after the termination is complete.

--Barry Finkel

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Hi Barry Ordinary users just let Firefox restore tabs. I have no idea what your awk script is or does but that may not take into account the Fx 33 changes & I am not sure you previously mentioned this complicating factor. What is wrong with just using Firefox's built n features ?

Firefox's sessionrestore system used to be fairly fragile and not have any useful backups. As explained in the blog that all changed with Fx33. You now have many effective snapshots of the sessinstore that you may try to use. As I stress please try using additional Firefox profiles if you need to consider restoring any such prior states, else you will just complicate matters and overwrite potentially relevant files.

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Yes, ordinary users (including me) let FF restore tabs. But other users do not have windows vanish upon restart, so they do not have to try to gather diagnostic information. I am trying to gather information that might let us determine what is happening. I, as a retired long-time systems programmer, am trying to determine what is happening.

The _____.js files are files in a special format. I cannot look at them in a text editor and determine the content therein. My awk script takes the file (that has no <cr><lf> characters) and formats it so that I can see each window and tab. I add line breaks to re-format the file so that it is readable.

I could start with a new profile, but when I resume a project that currently has a window, then I would have to re-create that window manually. And one window has about 170 tabs.

I will look at this problem later this weekend.

--Barry Finkel

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Barry, I have not looked at the files or their format, but for my purposes in trying to answer your question it is sufficient to know that when renamed they open in Firefox and display the expected open tabs.

Should you wish to gather diagnostic information, and maybe file a bug it may help if you are able to find some reduced testcase. I suspect you may be exceeding the design parameters of this feature judging by a previous helpdesk comment and if so it would be pointless filing a bug. In any event it is often worth discussing things before filing a bug in order to ensure the bug is valid, and likely to be something someone may be interested in fixing.

You would NOT need to

have to re-create that window manually

I fail to see what your problem is with using a new ADDITIONAL Profile. Consider for instance

  • A new clean profile - is Firefox crash free in that ?
  • A new profile with everything but your 170 tab window removed.
    Very easy to do:
    1. Just clone the current profile. (Or add the necessary sessionstore to a new profile).
    2. In the cloned profile : Close all the Windows other than the 170 tabs & close Firefox
    3. Reopen Firefox with that profile. It now has only those 170 tabs.
      No need to manually recreate 170 Tabs.
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Here is a partial reply.

1) If there are limits on the number of windows, then FF should document them and enforce them. I expect computers to be "reproducible:; if I have exceeded limit then I would expect FF to behave the same when I have exceeded that limit. FF should not work sometimes and not work other times.

2) If I shutdown cleanly, then sesssionstore.js will be used at re-start. If I am missing one or more windows and I do a clean "Exit", then the sessionstore.js file should reflect the state of FF before the clean "Exit. Either it reflects only the displayed windows or all the windows, even those that somehow are not displayed. I do not understand how FF can be missing one or more windows, then I do a clean "Exit" and restart, find windows still missing,, then do another clean "Exit" and restart, and then find all windows present. I am currently looking at my scripts that process the .js files to see if they are correct in their counts of "tabs" occurrences.

I will post more tomorrow after I do more research.

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My suggestion that you may be exceeding design specs is conjecture but based on Helpdesk comment /questions/1067958#answer-813831

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? Modified December 4, 2015 at 6:28:03 PM GMT by guigs
  • Did you test this out using Nightly as Helpdesk suggested ?
  • What values are you using for
browser.sessionstore.max_tabs_undo   (default=10)

browser.sessionstore.max_serialize_back (default=10) browser.sessionstore.max_windows_undo (default=3)

It is also on based on the observation that you have 12 windows open and one of those is a dormant 170 tab Window. I know we do have some metrics, but I am guessing that is stressing the System and Firefox and is not a typical usage pattern for Firefox.

IIRC cor-el suggested you backup your sessinstore folder or profile when you have problems, are yo doing that ? Do you then try reopening in a new profile with the renamed files, that at least gives you a workaround that should recovers a previous state with all your Windows.

One of my suggestions is that you split your projects over different Firefox profiles.Not a solution, but a workaround that may prevent some of these problems. Given your OOM crashes and other problems, using fresh profiles seems a good idea.

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