Firefox Preview Nightly is a developmental channel for new Firefox Preview releases. It is intended for advanced users only.
Nightly releases are not tested extensively before being published. They may be unstable; users can expect occasional crashes or data loss.
The Nightly channel allows experienced users and developers to provide feedback on features and performance to help determine what makes the final release.
Please email firstname.lastname@example.org
with your comments, or file a bug on : Github
Firefox Nightly automatically sends feedback to Mozilla. You can read more about telemetry privacy here