Firefox - Clear Cache Firefox - Clear Cache Option 1: While in Firefox, press ctrl + shift + delete to bring up the history window. Make sure the Time range to clear option is set to Everything. Make sure Cookies and Cache are checked. Click Clear Now. Please make sure to close completely out of your browser after the process is finished. Option 2: Click on the button with 3 horizontal lines that open the File menu. Choose Settings. Go to the Privacy & Security menu on the left, then hit Clear Data. Click Clear. Please make sure to close completely out of your browser after the process is finished. If clearing cache and cookies does not resolve browser issues, try refreshing Firefox Open Menu. Then, click Help. Click More troubleshooting information. Click Refresh Firefox on the right side of this page. Click Refresh Firefox in the confirmation window. Firefox will then restart, and this window will come up. Click Done. Firefox will reopen to this page. Choose whether you want all or some tabs reopened, and click Let's go!