Current as 11/17/2017 for Mozilla Firefox version 57
To clear the cache, cookies or history in Mozilla Firefox:
1. In the upper right corner of the Mozilla Firefox browser, click the Hamburger Menu (Open Menu) button (1), and select Options (2).
2. Click Privacy & Security (3) in the Left Hand Navigation Panel , and then click clear your recent history (4).
3. In the new window that opens, choose Everything from the drop down menu (5). Click the Chevron next to Details and make sure all of the following are checked (6)
Browsing & Download History
Form & Search History
Offline Website Data
4. Click Clear Now (7)