As of 2019, roughly 5% of the entire internet uses Mozilla Firefox as a browser. You're potentially reading these words in it. What you might not know is that the browser's very existence is kind of an anomaly, the result of a last-ditch corporate defensive maneuver. Back in the late '90s, dozens of programmers raced to make the Netscape browser open source before the competition gobbled them up in the first browser wars. Their efforts gave us Mozilla.