Tonight, Microsoft officially released Internet Explorer 9 to the public. If you’re eager for details on how to download and install the final bits, I’ll have them shortly. In this post, I’ll talk about what’s in the final release
Although only five weeks have passed between the Release Candidate and the final version available for download now, that time was well spent. Several bugs I had logged in the RC are fixed, and performance is noticeably snappier. And, somewhat surprisingly, two features that weren’t available in the RC made it into the final release:
  • IE 9 now supports the Do Not Track header that Mozilla proposed earlier this year. The feature is in addition to the much more active Tracking Protection feature that blocks third-party tracking sites. According to Rob Mauceri, Principal Group Program Manager for Internet Explorer, Do Not Track is implemented as a header and as part of the Document Object Model (DOM) API. As a result, says Mauceri, “sites can detect a user’s intention not to be tracked.”
  • The Tracking Protection feature now covers ActiveX controls—the most popular of which is Adobe Flash. In the final version of Internet Explorer 9,  requests from ActiveX controls go through the same Tracking Protection Lists that govern websites. If you’ve blocked a third-party site, it will be blocked for access in Flash and other ActiveX controls as well. I’ll need to test this feature to see if it has an impact on local shared objects–aka “Flash cookies.”
If you’ve already downloaded and installed the IE 9 Release Candidate you probably won’t notice any changes. The core of the IE 9 interface is the same as I described last month in my in-depth look at the Release Candidate.
In a follow-up post, I’ll look at how IE 9 compares with its archrivals, Google Chrome and Mozilla Firefox. Here’s the executive summary, broken down into four key categories.
Performance: “screamingly faster”
Last week, my colleague Steven J. Vaughan-Nichols benchmarked the performance of Google’s just-released Chrome 10 and called it “screamingly fast.” That conclusion was based on a set of benchmarks that mistakenly compared the unoptimized 64-bit version of Internet Explorer 9 to the 32-bit version of Chrome. When he re-ran the tests, IE 9 came out ahead. I guess that makes the new Internet Explorer “screamingly faster” and, at least for now, dethrones Chrome as the speed king.
My experience with the final release of IE 9 supports that conclusion. In tests on two high-end desktop systems using the SunSpider benchmark, IE 9 came out on top of the just-released Google Chrome 10 by a minimum of 11%. The release candidate of Firefox 4 actually outperformed Chrome ontwo of three systems but was still 12.6% slower than IE 9. On a notebook using an ultra-low-voltage Core 2 Duo processor, the difference was even more profound: Firefox 4 and Chrome 10 needed 24% and 29% more time to finish the benchmark than IE 9.
The most important measure of performance, of course, is the real world. So I set up a test bed with browsers arranged side by side on PCs with similar configurations and found the differences between the three leading browsers to be minimal in everyday use. On graphically intensive pages, IE 9 was often able to finish loading a page faster than Chrome. The difference was especially noticeable on systems using older GPUs. The only significant differences I found were on sites that use cutting-edge HTML5 features, where the difference came down to differences in how each browser handles an emerging standard.
Apparently, the designers of modern web browsers share a philosophy with supermodels: You simply can’t be too thin.
IE 9 follows that dictate to a fault, combining  the address bar and browser tabs into a single row that is significantly more compact than its rivals. Here, from left to right, are IE 9 in its standard one-row configuration followed by Chrome 10, Firefox 4 RC, and IE 9 with tabs on a second row.

When maximized, both Google Chrome and Firefox 4 RC shave the pixel count by eliminating the title bar—an odd-looking, decidedly nonstandard design choice that breaks one of the key Aero Snap window management capabilities in Windows 7. When there’s no title bar, you can’t drag a maximized browser back to a window but instead have to aim for the tiny Restore button in the top right corner.
The big design innovation in IE 9 is a feature called Pinned Sites, which lets you save a web shortcut on the taskbar and open that site as if it were a Windows app. Google Chrome has a similar feature called App Shortcuts. On Windows 7, the feature is useful, especially now that Pinned Sites can open multiple shortcuts in a pinned browser window. There’s no doubt that this feature is interesting, but it’s difficult to discover and I’m not sure the average Windows user will see the benefit. Something tells me that it will be much more useful in Windows 8.
Microsoft told me last week that it had signed up a slew of new partners that were planning to add Pinned Site support, including Groupon. In addition, some sites will reportedly offer free premium services for anyone who pins respective sites to the taskbar—Hulu promises a free month of its Hulu Plus service, and Pandora will reportedly have a premium offer as well.
Security and Privacy
Last week’s Pwn2Own test results provided at least one data point to suggest that Internet Explorer 9 is more secure than its predecessor. IE 8 fell, but only to an attacker who chained together three separate vulnerabilities in an attack that took six weeks to write. And Microsoft was able to announce, with some relief, that the final release of Internet Explorer 9 would have been able to withstand that attack. No one at CanSecWest wanted to take a run at either Chrome or Firefox, so they remain untested
Most of the other security improvements are under the hood and hard to quantify. The one that isn’t is the built-in protection against one of the most common forms of exploits. I see notifications at least once a day that Internet Explorer 9 has modified a site to prevent a possible cross-site scripting attack, which is reassuring.
As for privacy, I’ve already written at some length about how the new Tracking Protection feature in IE 9 works, and the initial crop of third-party Tracking Protection Lists haven’t changed since I looked at them last month. So far, these features qualify as a good start, but they’ll need significant third-party support—and maybe some legislative help—to get any serious traction.
The biggest weak spot for Internet Explorer 9 is compatibility. Ironically, it’s not a flaw with the rendering engine that causes most problems. Instead, the cause is legacy code on sites that target a specific Internet Explorer version and haven’t accounted for the possibility that Microsoft would one day ship a browser that doesn’t need a page full of hacks to display properly.
I’ve spent hours studying the different signals that websites and Internet Explorer can exchange with one another, and I came away with a splitting headache. More importantly, even after reading that I’ve found multiple sites that simply won’t display quite right in IE 9. On one page hosted at, the only way to get text to wrap properly was to press F12 and use the Developer Tools to send a different User-Agent string to the site.
One particularly interesting example of a tricky compatibility problem manifests itself on this amazing New York Times page that positions a slider in the middle of two side-by-side satellite images of cities in Japan that suffered heavy damage in the recent earthquake and tsunami. As you drag the slider, you can see the difference between the “before” and “after” images. The slider works perfectly in Google Chrome and Firefox 4 RC. But in IE 9, the images don’t change until you release the slider button, which ruins the fluid effect.
To make the slider work properly, you have to click the Compatibility View button in IE 9. Ironically, an inspection of the markup under that page reveals that it already includes a pinned_site.js file that targets IE 9, and the site is on Microsoft’s official Compatibility View list. Anyone who visits this page with IE 9 will be disappointed and might not realize that the page isn’t working correctly.
Over time, web developers will adapt, and many of these compatibility problems will vanish. The good news is that Microsoft is genuinely in this for the long haul.