- Launch Firefox.
- In the upper right corner of the Firefox window, click the hamburger menu. This brings up a dropdown menu with the majority of the browser options you may change without resorting to authorised browser hacks.
- Near the bottom of the screen, click Help.
- From the Help menu, select Troubleshooting Information.
- On the Troubleshooting Information screen, click Refresh Firefox in the top right corner.
- Mozilla will then notify you that you're about to uninstall all of your browser add-ons and revert to the default settings. To put it another way, you're about to undo everything you've ever done in the browser. To continue, click Refresh Firefox.
You'll see a success screen after Mozilla refreshes the browser. To continue using the browser in its default mode, click Let's Go.