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Firefox 13 (Released June 5, 2012) has introduced a new default setting to Load Tabs on Demand. This causes the browser to only restore the currently selected tab when resuming a session on startup, after a crash, or on a requested reload. I really don't like how I now have to click each tab and select restore.
How can I turn this off?
You can turn off the new default setting within the options panel.
Options
General Tab click the option drop-down next to When Firefox starts: and choose Show my windows and tabs from last time
Don’t load tabs until selected option and press OK
browser.tabs.loadInBackground in about:config does not do it.
Jun 23, 2020 at 11:07
One small addition to Jeremy's answer is that after you've unchecked the checkbox, you can switch back to one of the other options in that dropdown and keep the setting.
This is useful for people that don't save their tabs by default in cases like restarts caused by extension installations where your tabs do get saved.
And if you're using Tab Mix Plus (TMP), you need to go to TMP Options > Session > Restore and check the "Reload all tabs" checkbox (which respects the Load Tabs Progressively add-on if you're also using it).
Not sure about what needs to be done if you're using the Session Manager add-on.
/kim
