Mozilla today released Firefox 5, three months to the day after Firefox 4 was released. The new Firefox 5 release marks the successful debut of Mozilla's rapid release process, which iterates new releases every three months.
Firefox 5 includes new performance, standards and privacy improvements as well as improving the overall stability of the browser for Windows, Mac, Linux and Android users.
"Firefox 5 is the fastest Firefox ever, and also the fastest ever to market," Johnathan Nightingale, Director of Firefox at Mozilla told InternetNews.com. "Our new rapid release cycle means that the improvements get into users hands more quickly. The latest version of Firefox includes more than 1,000 improvements and performance enhancements that make it easier to discover and use all of the innovative features in Firefox. "
Among the changes is improved visibility for Mozilla's Do Not Track implementation. With Firefox 5, users can now use an interface item to select whether or not they want websites to track them. Firefox has been supporting a Do Not Track implementation since the Firefox 4 release, though with Firefox 5 it is now user visible. Firefox's Do Not Track is a simple binary expression -- when enabled, it sends an HTTP header that says, DNT=1, which means: "do not track me."
On the developer front, Firefox 5 supports CSS animations, allowing for a new generation of 'Flash-free' web interfaces. Mozilla is also debuting the Firefox Add-on SDK as a tool to help build restart-less next generation add-ons for Firefox. The Add-on SDK is part of the project formerly known as Mozilla Jetpack.
From a performance perspective, Firefox 5 includes a number of HTTP optimizations that help to accelerate content. One such optimization is the Sort Idle HTTP Connections by CWND feature. The HTTP optimization helps to reduce the roundtrip time taken by HTTP transactions by efficiently utilizing the congestion window (CWND) inside of HTTP.
"We've been taking a look at optimizing some of the fundamental building blocks of the Web and you're seeing that start to pay off in the next version of Firefox with our changes to request headers and connection management," Nightingale said.
Mozilla is not the only browser vendor that is looking at optimizing the transport layer of the web. Google has its own TCP optimization layer called SPDY, which could potentially be leveraged by Mozilla at some point in the future.
"As for SPDY, there's some work left to do on standardization, but we're very interested," Nightingale said. "It looks like a decent evolution for HTTP without changing the app model. We don't know if or when we're going to ship it, but we're interested in spending time implementing it."
In terms of the upgrade path for current Firefox users, Nightingale noted that Firefox 4 users will start seeing the updates today.
"Once that initial wave subsides, we'll make it available to 3.6 users who explicitly check for updates from their help menu," Nightingale said. "Once we determine that we want to address the rest of our users on 3.6, we'll put together a prompted update to let them know about Firefox 5 and encourage them to upgrade."
In contrast with the long development cycle for previous Firefox releases, which often resulted in longer lists of user-facing features that took a long time to deliver, the new rapid release cycle is about delivering features faster.
"Over time, users will notice that our rapid release development cycle delivers new features, performance enhancements and security and stability improvements faster," Nightingale said. "Users won't have to wait to experience the best the Web has to offer. With every regular update, users are going to get a faster, more stable, and richer browsing experience."
The process of moving from a feature-based release cycle to a time-based cycle has been a major transformation for Mozilla.
"Frankly, it's been surprising to see how quickly the entire project has re-organized and shifted from major releases to a rapid release schedule," Nightingale said. "We're incredibly proud to ship Firefox to hundreds of millions of users worldwide while maintaining the high standard of quality users have come to expect from Mozilla."