Firefox Extended Support Release (ESR) is an official version of Firefox developed for large organizations like universities and businesses that need to set up and maintain Firefox on a large scale. Firefox ESR does not come with the latest features but it has the latest security and stability fixes.
To autodelete cookies when cookies aren't being used when switching a tab install Cookie Autodelete
For better privacy use TOR Browser.
TOR Browser was developed to do the following:
- BLOCK TRACKERS
- DEFEND AGAINST SURVEILLANCE
- RESIST FINGERPRINTING
- MULTI-LAYERED ENCRYPTION
- BROWSE FREELY
TOR Project Mission statement:
To advance human rights and freedoms by creating and deploying free and open source anonymity and privacy technologies, supporting their unrestricted availability and use, and furthering their scientific and popular understanding.
Browser hardening boils down to editing Browser settings to disallow Websites to track your activity among other things.