You can always Delete browsing, search and download history on Firefox If you want or need to clear your history every time you use Firefox, you can set it to happen automatically on exit, so you don’t forget. Click the menu button and select Settings. Select the Privacy & Security panel and go to the History section. In the drop-down menu next to Firefox will, choose Use custom settings for history. Check the box for Clear history when Firefox closes. For more info you can read that article https://support.mozilla.org/en-US/kb/delete-browsing-search-download-history-firefox#:~:text=older%20macOS%20versions).-,Click%20the%20menu%20button,be%20cleared%2C%20click%20the%20Settings%E2%80%A6