To reset master password in Firefox, you can follow these steps:
1. Open Firefox browser and type this in URL bar.
2. Now press enter and “Reset Master Password” page will appear. In this page, click on the reset button to reset the master password of Firefox.
3. Then a pop up box will be there which asks for your confirmation. Click on OK.
Next time, when you will start Firefox, it will not ask for the master password. Now you can set a new one.