The move to 64-bit software has been steady (if slow), but browsers are in their own category entirely. Microsoft has been offering a 64-bit version of Internet Explorer (IE6 and up) since the release of the 64-bit versions of Windows XP and Windows Server 2003 in April 2005. A 64-bit version of Safari is available in Snow Leopard, and Linux users can download a 64-bit version of Opera.

Chrome, however, doesn't yet have a 64-bit version. Firefox has one, but only for Linux (unofficial 64-bit versions of Firefox exist for Windows and Mac).

So why haven't Mozilla and Google bothered to release official 64-bit browsers? For the same reason Microsoft hasn't bothered to produce a 64-bit version of its Silverlight plugin: nobody uses 64-bit browsers.

The 64-bit conundrum



That might sound like a vicious circle, and it is; if you are using a 64-bit browser, you need to use 64-bit versions of all your plugins, and plugin makers aren't particularly eager to make 64-bit versions until 64-bit browsers start being used with some frequency. There are three key plugins that need to offer 64-bit versions before mainstream users can switch. In order of least important to most important, these are: Silverlight, Java, and Flash.

Although Silverlight is nowhere near as important as other plugins, after releasing a beta of version 4 Microsoft did say that its Flash alternative had about 45 percent penetration so far (which is quite impressive, given that Silverlight isn't even three years old; its use by Netflix certainly helps that figure). A 64-bit version, however, is still not in the works.

In February 2009 we e-mailed Scott Guthrie, corporate vice president of Microsoft's .NET Developer Division, and asked him if Silverlight 3 would have a 64-bit version. He told us no, as other browser plugins (and most browsers) don't support 64-bit. Silverlight 3 was released in February 2009 and indeed was only available for 32-bit browsers.

Soon after the Silverlight 4 beta arrived (unsurprisingly, only in a 32-bit version), we spoke with Brian Goldfarb, director of the Developer Platform and Tools Group at Microsoft, about the company's priorities for developing future versions of the plugin.

"The simple answer is no, we are not supporting 64-bit browsers," Goldfarb told us. "Users are running 32-bit browsers because of plugins. It's all about sequencing and timing. We're absolutely going to do it; we're just not going to do it yet." Based on the data Microsoft was seeing, 64-bit browser support just wasn't worth the effort, Goldfarb told us.

"I don't know at what version, but it will happen," he said. "My customers are asking for other features. We need to bring people into the 64-bit world, but the tradeoffs aren't worth it right now. Businesses aren't asking for 64-bit."

Java, on the other hand, added 64-bit support 12 months ago: Java SE 6 Update 12 was released in January 2009 (almost four years after the first 64-bit version of IE arrived). Flash, arguably the most important plugin for day-to-day browsing, doesn't have any 64-bit support except for an alpha Linux version released in November 2008.

But support for 64-bit browsers isn't something that can really be touted as a competitive advantage at this point in the game; it simply wouldn't faze Adobe to see the competition offer it. The only official statement the company offers on its website is a TechNote titled Flash Player support on 64-bit operating systems, which was updated on October 21, 2009:

Issue: Adobe Flash Player is not supported for playback in a 64-bit browser. However, you can run Flash Player in a 32-bit browser running on a 64-bit operating system. Reason: Adobe is working on Flash Player support for 64-bit platforms as part of our ongoing commitment to the cross-platform compatibility of Flash Player. We expect to provide native support for 64-bit platforms in an upcoming release of Flash Player following the release of Flash Player 10.1.

Why use 64-bit browsers anyway?

While a move to 64 bits doesn't noticeably impact browser performance, 64-bit browsers are more secure... at least for now.

"Security is a huge priority for us, and Silverlight has had virtually no security issues," Goldfarb noted. He also agreed that there is clearly a temporary gain for switching to 64-bit browsers; eventually malware writers will go where the majority of users are anyway. There really wouldn't be much of a long-term gain, but the short-term gain, which could last a few years, is worth the effort since the larger majority of malware is written with the assumption the targeted browser is 32-bit.

Furthermore, techniques such as Address Space Layout Randomization (ASLR), a security technique which involves randomly arranging the positions of key data areas in memory to thwart hacking, can currently be defeated on 32-bit browsers through techniques such as heap-spraying, which some exploits use to execute arbitrary code. Malicious programs can thus fill the program's address space with malicious code so that even if a random memory address is chosen, there is still an excellent chance that the exploit code is executed. Heap-spraying and other malware methods aren't as viable with a large, 64-bit memory space.

Making 64-bit the default

Along with Windows 7, Windows Server 2008 R2 hit RTM on July 22, 2009. This is the first 64-bit only Windows server operating system, and many are expecting Windows 8, which is currently slated for 2012, to be the first 64-bit only Windows client OS.

That means Microsoft has about three years to push support forward so that when Windows 8 and its server counterpart finally arrives, the company can finally flip the switch and set the 64-bit version of Internet Explorer 9 as the default. Maybe that's just wishful thinking, but a lot can happen in three years.