Mozilla introduced tabs on demand in Firefox 8 which added “don’t load tabs until selected” option (not enabled by default) to General tab of Options, Mozilla enabled it by default from Firefox 13 release onwards. Tabs on Demand is part of Snappy project which doesn’t restores tabs until chosen by the user, remember this feature applies to Firefox only when Firefox set to “show my windows and tabs from last time” under Startup.
There are benefits with this and also a slight disadvantage to the user where user needs to select every tab from the last session to load which may be discomforting to him/her. And on the other hand advantage user has with this feature is Firefox becomes more responsive and startup times are also improved because Firefox has to load only user’s last facing tab in the background.
If you don’t want this feature and like to see Firefox loading all tabs on startup without your interaction, then you can easily turn off this feature and how that can be done explained below with step by step.
To disable tabs on demand or to load all tabs on startup from last session
1. Firefox button >Options> Options
2. Select Tabs tab and uncheck for fifth entry from top Don’t load tabs until selected,
3. Click Ok to save the changes to Firefox.