Clear Cookies and Cache in Firefox on iPhone
The controls to clear your Cookies, Browsing history, cache and other data in Firefox are all stored in the same screen. To get to these controls and choose what you want to clear, follow these instructions.
These screenshots are taken in Firefox on Windows but the process is identical on Mac and Linux computers.
Click the Firefox menu button
Click the button that looks like three horizontal lines in the top right corner of the Firefox window.