Firefox from Mozilla turned 5 this month, and celebrated by having achieved 25% of the global browser usage market share. NetMarketShare.com from Net Applications tracks global and local usage market share for browsers, operating systems, search engines and mobile systems.

“What an exciting milestone for Mozilla, particularly as we are celebrating five years of Firefox this week,” said Mitchell Baker, Chair, Mozilla. “The momentum around Firefox adoption has been truly astounding.”

When Firefox entered the browser wars, we at Net Applications always asserted it needed to achieve 10% usage market share to be considered a true competitor to Microsoft’s Internet Explorer. Mozilla crossed that threshold back in March of 2006 and they have grown their usage share fairly steadily since then. Now 1 in 4 people globally are browsing the Internet with Firefox.

That’s impressive, especially when you consider the advantages the other browser providers have enjoyed over the years:

• Internet Explorer has been the default browser on Windows systems, and often the only browser supported by many company’s IT departments
• Safari has been the default browser on Macs and iPhones
• Opera has often been first to introduce new browser features, and has supported many mobile and gaming devices
• Chrome comes from Mozilla’s primary source of revenue, Google, and has performance advantages over other browsers

The competition has been heated, but Mozilla has focused on a formula of:

• Free (this may seem obvious now, but there had to be a difficult decision made between charging for the browser as Opera was doing early on, or come up with another revenue model)
• Open source
• Extensibility
• Excellent user experience
• Frequent updates and innovation

That formula has been successful so far, but the war is far from decided. Microsoft’s release of Windows 7 has seen a very impressive early adoption rate. There are 2 major decisions computer users will face with a major new operating system available. First, do they upgrade to Windows 7, or is this the time to consider an alternative such as a Mac OS or Linux based system. New Mac users will most likely lead to new Safari users. Second, with a new operating system many people will have to decide on a default browser again. This gives IE a great opportunity to win back some of its lost market share. But, it also gives Chrome, Opera and other browsers an opportunity to become the alternative browser of choice over Firefox.

Another major force in the browser wars is the move to mobile. The iPhone has proven that people will browse from their mobile device if the browser and device can provide a similar user experience to a computer. Mobile browsing is projected to grow substantially in the years to come, so this may be the next big battle ground for browser providers.

See current usage market share and trends at NetMarketShare.com.

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