June brought the first result of Mozilla's new Rapid Release strategy for Firefox. Firefox 4, just three months old, was superceded by the all-new but not-too-different Firefox 5. Firefox's market growth was all but ended by the release of Chrome, and Mozilla is hoping that by adopting a similar release schedule to Google, it will be able to reignite the growth of its user base.

Internet Explorer is down 0.59 points at 53.68 percent. Firefox is essentially unchanged, down 0.04 points to 21.67 percent. Chrome is up 0.59 points to 13.11 percent. Safari is also up, gaining 0.2 points to reach 7.48 percent. Opera dropped 0.3 points to 1.73 percent.

The trends established over the last few months are continuing: Firefox is treading water, while Internet Explorer is losing users, which seem to be being picked up by Chrome. In the past two months, Opera has dropped 0.41 points—that's a loss representing 20% of its market share. Our own Ryan Paul liked Opera 11.50, which was released just a couple of days ago, so perhaps this will help turn around a perilous slide.

Looking at individual versions, Internet Explorer 6, 7, and 8 are all down, by 0.18, 0.46, and 1.21 points respectively. Internet Explorer 9 made strong gains, of 1.44 points, but not enough to undo the losses. Internet Explorer 9's gains seem to be occurring at the expense of older versions—Internet Explorer 8 on Windows 7, versions 7 and 8 on Windows Vista—rather than making converts of the other browsers.

Internet Explorer 9 is of course at something of a disadvantage, as it won't run on Windows XP. While we agree with the decision to cut Windows XP off, one consequence is that not a single Internet Explorer 6 user can upgrade to Internet Explorer 9. Nor can anyone using Internet Explorer 7 or 8 on Windows XP. If the focus is narrowed from all users to just those using Windows 7, the Internet Explorer 9 situation looks a little more promising. Though Internet Explorer 8, which ships with Windows 7, commands the highest market share, at 38.47 percent of Windows 7 users, Internet Explorer 9 takes second place, at 15.61 percent—putting it ahead of Firefox 4 and Chrome 12, at 13.74 and 11.60 percent, respectively.

Internet Explorer 9 seems, therefore, to be performing well among users of Microsoft's latest and greatest operating system; it's just that only 27 percent of the global audience is running that platform. Windows XP still commands a slim majority, with a global share of 51 percent. As Windows XP declines and Windows 7 grows, we can expect to see Internet Explorer 9 lifted by this transition.

Firefox versions 3.5 and 3.6 both saw drops last month, by 2.06 and 0.28 points, respectively, and versions 4 and 5 rose by 0.38 and 2.05 points, respectively. This suggests that the transition from "old" Firefox (3.x) to "modern" Firefox (4 and 5) is slowing down; in May, the 3.x versions dropped by an aggregate of more than 4.5 points, with the then-current Firefox 4 picking up all of those users. This month, only around half as many users made the switch. Though "modern" Firefox versions are now used by a majority of Firefox users, it looks like a hard core of "old" users is going to stick around. Over the next few months, we can expect Firefox 3.5 to decline more heavily, as Mozilla intends to push out a patch that will upgrade users to the newest 3.6 version.

Chrome as ever shows rapid migration between versions. Over the course of June, the browser's stable version went from 11 to 12, and the rapid cutover we've grown to expect occurred. However, that transition isn't complete. 1.39 percent of users are on Chrome 10 or older, and it looks like Google's generally seamless automatic upgrades aren't touching these users. The source of these users isn't clear, though there a few plausible explanations. Obviously, some individuals and corporate users may simply have opted to disable the updates. Automatic updating is the default, but it can be turned off. Though this gives these users and enterprises greater control over the browser version they're using, this comes at some risk; Google doesn't have security updates for old versions of Chrome, so these people are using browsers with known exploitable flaws.

Chrome's automatic updating is also dependent on a system service. Though the browser can be installed by non-administrators, installation of the service requires administrator privileges. Unlike Firefox, which checks for and performs updates within the browser itself, Chrome depends on its service to do this task. If the service doesn't exist, updates don't happen.

That's probably not enough to account for every legacy Chrome user, however. To do that, we probably have to look towards the East Asian market. A long-standing feature of various markets in the region, most notably China and South Korea, is the entrenchment of Internet Explorer, variously attributed to legal mandates (especially in South Korea, where until last year a specific ActiveX control was required for online banking) and widespread software piracy making users reluctant to use Windows Update (even though Internet Explorer upgrades are available to pirated copies of the operating system).

To support this market, a range of browsers based on Internet Explorer's rendering engine, but with substantially greater features, sprung up. The most popular of these are 360 Secure Browser with about 19 percent share of the Chinese market, and Sogou high speed browser, with a little under 6 percent. Though these browsers originally just used the Trident engine that powers Internet Explorer, recent versions extend this by also embedding Chrome. In so doing, they give their users a choice between a relatively modern Chrome browser engine, and the older Internet Explorer engine needed for compatibility. Conceptually, this is very similar to software like Chrome Frame, that allows Internet Explorer users to use Chrome for some browser tabs.

These dual-engine browsers tend to modify Chrome in several ways, one of which is that they exclude Google's automatic update service. They also tend to embed stale versions of Chrome; the current Sogou uses Chrome 6. The result is that users of these browsers, who may well prefer using Chrome for day-to-day browsing, will be stuck with obsolete versions of the browser. And because of the way they're using Chrome, they're out of reach of Google's update system.

The net result of these various usage scenarios is that Chrome's non-upgrading userbase is likely to grow ever larger, with ten percent of Chrome users, and climbing, sticking with versions of the browser that are no longer supported.

Ars' audience continues to show marked differences from the Internet's norms. Firefox, Safari, Internet Explorer, and Opera all saw drops, of 0.94, 0.37, 0.04, and 0.10 points respectively; Chrome saw gains of 0.88 points, with the remainder of the difference picked up by "other."