Warning: Nightly is an unstable testing and development platform. By default, Firefox Nightly automatically sends data to Mozilla — and sometimes our partners — to help us handle problems and try ideas. Learn what is shared: https://www.mozilla.org/en-US/privacy/firefox/#pre-release
Firefox Nightly gets updated every day and is designed to showcase the more experimental builds of Firefox. The Nightly channel allows users to experience the newest Firefox innovations in an unstable environment and provide feedback on features and performance to help determine what makes the final release.