Mozilla Firefox maintains its position among the top browsers, while continuing to boast its signature full-featured and open browsing experience. Though it might not have been the pioneer of such concepts like tabbed browsing, it was a catalyst for bringing the concept to mainstream audiences. These features are complemented by an impressive library of over 10,000 extensions that add even more functionality and value to users, thanks to its robust browser. The more recent releases have brought significant improvements to managing memory usage, and Firefox's private-browsing features have gotten more advanced, as well.
Firefox has also ramped up its Social API in recent versions, allowing for direct connections with the Facebook platform; version 21 opens up more networks to connect with by integrating MSN Now, Cliqz, and Mixi services directly into the browser interface. The "Do Not Track" privacy features in Firefox have also been updated, bringing new "neutral" default settings; that means neither "track me" nor "do not track me." However, it's still unclear how the default setting will behave any differently than picking "track me."
Version 21 also adds a monitoring tool called "Heath Report." The Health Report includes a Raw Data feed showing every item that's been scanned and tracked. This graphical representation of browser performance is designed to give users valuable data about startup time, extensions, crashes, and uptime--as well as send data back (if allowed by the user) to Mozilla to help the Firefox team build a better browser. Firefox also allows users to toggle sharing off--via a huge "Data Sharing" button at the top of the interface, or users can disable the entire Health Report via Tools > Options > Advanced > Data Choices.