GNUZilla Icecat is a fully-free fork of Mozilla Firefox ESR.
Extensions included to this version of IceCat:
Blocks privacy trackers while in normal browsing mode, and all third party
requests when in private browsing mode. Based on Adblock Plus.
Adds a custom "about:icecat" homepage with links to information about the
free software and privacy features in IceCat, and check-boxes to enable
and disable the ones more prone to break websites.
Uses the native video player to play embedded videos from different sources
* Fingerprinting countermeasures: Fingerprinting is a series of techniques
allowing to uniquely identify a browser based on specific characterisics of
that particular instance (like what fonts are available in that machine).
Unlike cookies the user cannot opt-out of being tracked this way,
so the browser has to avoid giving away that kind of hints.