Private Browsing in Firefox allows a person to browse the Web without storing local data that could be retrieved at a later date. To disable browsing history and the web cache in Firefox, do the following:
Step 1: Click the three horizontal lines near the top right hand corner of the browser to open the menu
Step 2: Select the second option down the menu New Private Window
Step 3: Once clicked on, a new window will appear that has a darker colour scheme rather than the standard white colour scheme.
Now that you have opened the private window you will be able to browse the internet without anything you have done previously in Firefox affecting it.
When you have finished browsing, as soon as you close the private window, all your browsing history and/or credentials you have used will be wiped.