The System Detail list next to your question shows that you run an older Firefox 43 version that is no longer supported with security updates. Always update Firefox and Add-ons to the latest versions to get all security fixes.

Please update to the current Firefox 44.0.2 release.

• Help > About Firefox
• https://support.mozilla.org/kb/update-firefox-latest-version

You can check browser.sessionstore.* prefs like browser.sessionstore.resume_from_crash on the about:config page. You can reset browser.sessionstore prefs that are user set (bold) via the right-click context menu to the default value to make sure that Session Restore is enabled and working properly.

• http://kb.mozillazine.org/Session_Restore
• https://support.mozilla.org/kb/restore-previous-session
• http://kb.mozillazine.org/browser.sessionstore.resume_from_crash

You can use this button to go to the current Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)
• http://kb.mozillazine.org/Profile_folder_-_Firefox

I update Firefox to the newest 44.0.2 And go to about:config, change the value of "browser.sessionstore.resume_from_crash" from user set to default.

But after I restart Firefox, the problem remains. Only 11 pages can be kept.

However, when I go to C:\Users\XXXXX\AppData\Roaming\Mozilla\Firefox\Profiles\XXXXX.default, I find a BAK file called "sessionstore". I open it with txt and I find that all of the pages are kept.

The question is why they doesn't show in the tab?????

Any Moderator? Anyone? Moderator only reply to fresh posts?

Current Firefox versions do not use sessionstore.bak There is only a sessionstore.js that is created when you close Firefox.

Firefox can keep a lot more tabs than 11.

Start Firefox in Safe Mode to check if one of the extensions (3-bar Menu button/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem.

• Switch to the DEFAULT theme: 3-bar Menu button/Tools > Add-ons > Appearance
• Do NOT click the Reset button on the Safe Mode start window

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

Firefox uses the sessionstore.js file in the profile folder to store session data, but this file is only present when Firefox is closed. The sessionstore.js file is created from recovery.js when you close Firefox and is removed and copied to previous.js when you start Firefox to make is possible to restore the session at any time.

Backup the session files in the sessionstore-backups folder in the Firefox Profile Folder to make sure not to lose possible important session data. Do NOT close Firefox when Firefox is already running.

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).

See also:

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

I start Firefox in Safe Mode but it can't solve the problem.

I also turn all Plugins into "Never Activate" then start Firefox into safe mode. However, there were only 11 websites kept in one tab.

I replace "sessionstore.js" with "upgrade.js-<build_id>". Find that more than 15 websites are kept in one tab. But after I restart Firefox, some of them disappear and only 11 websites remain in the tab. Then I move the original "sessionstore.js" back into the folder.

Moderator?

Current Firefox versions only store a maximum of 10 entries of tab back history as part of stored session data in the sessionstore.js file. So you lose tab back history beyond those ten entries when you use "Show my windows and tabs from last time" to restore open tabs on the next start.

The default for max_serialize_back is 10. A value of -1 will disable this maximum and allows to keep all back history entries.

• browser.sessionstore.max_serialize_back

You can open the about:config page via the location/address bar. You can accept the warning and click "I'll be careful" to continue.

• http://kb.mozillazine.org/about:config

OMG it works!!!!!!!!! Restart Firefox twice and it works! All the pages are kept!

Thank you thank you thank you.

Actually, I was thinking to quit Firefox if this problem can't be fixed. Thank you.

But I wonder why Firefox sets the number to 10? That is too less and not acceptable. Could you report my situation to designers/admin/someone else for improving Firefox? But whatever Anyway Thanks for your help.

Glad it helped. I will mark the thread solved.

You can make that suggestion yourself.

However IIRC that is a fairly recent change, and has a config option to disable it. I very much doubt it will be considered increasing the number, I am sure research would have been done on the number of back history tabs that were likely to be useful or used, compared with the overheads of keeping that.

Use

• https://input.mozilla.org/feedback
• forums
  • See etiquette
  • Maybe use wishlist

P.S. Potentially useful tip:

Have you thought of using bookmarks.

You may keep hundreds of bookmarks,maybe put some of them as nested dropdown folders on the bookmarks toolbar. Or even a move the bookmark tool bar items to the navigation bar if that has space.

• Use bookmark folders to organize your bookmarks
• Bookmark Tags - Categorize bookmarks to make them easy to find
• Bookmarks in Firefox
• Address bar autocomplete suggestions in Firefox_changing-results-on-the-fly