Developer's DescriptionBy MozillaBe among the first to explore future releases of Firefox browser.Test brand new features of Firefox browser daily (or... nightly). Enjoy at your own risk.Every day, Mozilla developers write code that is merged into a common code repository (mozilla-central) and every day that code is compiled so as to create a pre-release version of Firefox based on this code for testing purposes, this is what we call a Nightly build.