I'm not an expert but i think you can edit this value in `about:config` and change the value of `browser.sessionstore.max_tabs_undo` from 10 to whatever suit your needs.

Harest said

I'm not an expert but i think you can edit this value in `about:config` and change the value of `browser.sessionstore.max_tabs_undo` from 10 to whatever suit your needs.

In this response was the kernel of what is needed to change the settings.

First - - place 'about:config' in the url bar.

  (this took some looking to find as its not clear where this file resides)

Second - - -scroll down (waaaaaaaaaaaaay down) and then when the needed item is found highlight the line. Third - - - a right-click (IIRC) offered the option of 'modify'

    (needs to be the value that you want to change)

Fourth - - - the desired change can be affected.

What is so surprising is that no one has asked this particular question before. I guess there aren't many people who use their browsers for more than a handful of tabs at once and then rarely save nor close them.

Thank you to the responder for the information. My added response was to make the method of change clear for anyone who doesn't live in the 'Firefox' environment.

Note that the about:config page comes with its one sidebar, so just type max_tabs You can double-click a line to modify this pref.

Type about:config in the location (address) bar and press the Enter key to open the about:config page like you open a website by typing the URL in the location bar.

• if you see a warning message then you can confirm that you want to access the about:config page.

• use the Search bar at the top of the about:config page to locate preferences more easily
• preferences that have been modified and do not have the default value show as bold (user set)
• preferences that are user set (bold) can be reset to the default value via the right-click context menu
• preferences can be modified via Modify (String or Integer) or Toggle (Boolean) in the right-click context menu and by double-clicking the line with the pref
• preferences can be created via the right-click context menu: New -> String, Integer, Boolean

See also:

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

Note that there is a pref for windows as well. browser.sessionstore.max_windows_undo

See also some sessionstore prefs like:

• browser.sessionstore.max_serialize_back (10)

dabeegmon said

What is so surprising is that no one has asked this particular question before. I guess there aren't many people who use their browsers for more than a handful of tabs at once and then rarely save nor close them.

This is mentioned in at least a few threads each year, but the search feature of this site is... not very good. (Mine's set to 20, for what it's worth!)