You may have a corrupt xulstore.json file.

Type about:support in the address bar and press enter.

Under the page logo on the left side you will see Application Basics. Under this find Profile Folder. To it’s right press the button Show Folder. This will open your file browser to the current Firefox profile. Now Close Firefox.

Locate the xulstore.json file. Then rename or delete it. Restart Firefox.

It is probably best to try testing in a new additional Firefox profile created just for test purposes.

You can try that with and without the addon, and in Firefx's safemode, which will disable the addon. You can also try with default settings of preferences in safe mode (Use of History tweak could change preferences and not reset them itself) See

• Profile Manager - Create, remove or switch Firefox profiles
• Diagnose Firefox issues using Troubleshoot Mode
  Safe Mode does not reset preferences you have changed.
• Reset Firefox preferences to troubleshoot and fix problems

dRyWyRd said

No matter what input I set browser.sessionstore.max_serialize_back and browser.sessionstore.max_entries remain stuck to the integer value of 999998.

I have recently installed Back/Forward History Tweaks. (https://addons.mozilla.org/firefox/addon/back-forward-history-tweaks/) Could settings be influenced by it.

If you can no longer set those to a reasonable number, then I would suspect the extension is trying to max them out so it can manage them. Does it have any settings to use a more reasonable number??

Before exiting Firefox, could you make a copy of your live session history file, recovery.js, for possible analysis?

You can 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.

Scroll down and double-click into the sessionstore-backups folder. Save the recovery.js file to a safe location, such as your Documents folder.

To confirm that the missing "back" history actually is stored in the live file, you can open the file in Firefox's "Scratchpad" tool (see: https://developer.mozilla.org/docs/To.../Scratchpad). There is a button to load a file, and you can point it to the backup, and after it loads, click the Pretty Print button to lay it out in a structured fashion. (example screenshot attached)

Find a tab that you have been working in, and you should see all of the URLs in history for that tab. Or is it already limited to 10?

FredMcD said

You may have a corrupt xulstore.json file. ... Locate the xulstore.json file. Then rename or delete it. Restart Firefox.

Is that a safe move? I assume Firefox will replace it with a default!?

jscher2000 said

If you can no longer set those to a reasonable number, then I would suspect the extension is trying to max them out so it can manage them. Does it have any settings to use a more reasonable number?? Find a tab that you have been working in, and you should see all of the URLs in history for that tab. Or is it already limited to 10?

I had set the extension to 999 (maximum) but I kept both browser.sessionstore.max_serialize_back and browser.sessionstore.max_entries to 100 (when it was still accepted).

I was considering whether I have been misleading using cut off in the title. URLs in the tab's history is working okay. Tabs showed in the dropdown list regularly exceed 11 (maybe going all the way to 999998, who knows?), that as long as I don't restart the browser.

Is will try to deactivate Back/Forward History Tweaks and see what happen.

The terms tests freaks me out..

I think:

• browser.sessionhistory.max_entries governs the maximum tab history during your session
• browser.sessionstore.max_serialize_back governs how much back history is available when the session is restored

It sounds as though browser.sessionstore.max_serialize_back is being ignored. I wonder whether that is because it is too large?

dRyWyRd said

Is that a safe move? I assume Firefox will replace it with a default!?

In all cases, files removed from the profile folder are replaced using default.

Try to set max_serialize_back to -1

• browser.sessionstore.max_serialize_back = -1

As I suspected, the bug disappears once Back/Forward History Tweaks is disabled. Apparently the extension take over on those values the instant it gets installed/activated. But why..? It should just enlarge the dropdown list. This way it becomes useless..

Could you guys have a try on your browsers too?

Contact its support page and tell them about it.

dRyWyRd said

Could you guys have a try on your browsers too?

Um, based on your experience, I'd rather not! But I could create a test profile and import my session history into that one, and install the extension there for testing. Maybe after hours.