This blog is closed as of 2/2015. @EricLaw left Microsoft in 2012, but was named an IE MVP in '13 & an IE userAgent ( in '14.

Q&A: 64-Bit Internet Explorer

Q&A: 64-Bit Internet Explorer

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From time to time, folks ask a variety of questions about 64bit IE.  I hope to answer the most common questions here.

NEW: Internet Explorer 10+ uses x64 in a fundamentally different way than IE7, IE8, and IE9, the versions for which the post below was written. By default, IE10+'s frame/manager process runs at 64bit, while Desktop Tab processes run in 32bit. Metro-style tab processes run at 64bit. A 64bit JIT was added to improve performance. You can learn more by reading a newer post.

Q: Can I install a 32bit version of IE on a 64bit version of Windows?

A: When you install the 64bit package, the 32bit version of IE will also be installed automatically.  You cannot install only the 32bit version on a 64bit operating system, because Internet Explorer updates OS platform components and must update both the 32bit and 64bit versions.

Q: As an end-user, how can I tell what bitness of IE I'm currently using?

A: To see if you're running the 64-bit version of IE, hit ALT+H to open the "Help" menu, and click "About Internet Explorer."  If you're running the 64bit version, this screen will say "64bit Edition." Alternatively, check out the x64 button add-on.

Q: From the server or from JavaScript, how can I tell what bitness of IE a web visitor is using?

A: The simplest method is to check the user-agent string.  See for more info.

Q: Why isn't 64bit IE the default browser?  Why can't I set the 64bit version of IE as the default browser?

A: This was an explicit choice made by the IE team, which may change at some point in the future.  The problem is that users might inadvertently get "stuck" using the 64bit version and not realize it.  This might cause some problems.

Q: Why?  What does not work properly with 64bit IE?

A: Browser addons, including BHOs, Toolbars, and ActiveX controls, must generally be the same bitness as IE itself.  So, if you are running a 64bit version of IE, any site that uses, say, Adobe Flash, isn't going to work until you install the 64bit version of the addon.  Sadly, almost no browser addons are currently available in 64bit versions, although that's somewhat likely to change in the future as 64bit Windows becomes more prevalent. 

There are two 64bit add-ons that I do recommend:

  • The 64bit version of Ralph Hare's most excellent mouse gestures addon
  • My x64 button, which allows you to easily recognize 64bit IE and reopen the current page in 32bit IE

 Q: What options/settings are shared between 32bit and 64bit IE?

Generally speaking, 32bit and 64bit share configuration settings wherever possible.


  • Homepage and favorites
  • Search providers
  • Web slices
  • Accelerators
  • Context Menu Extensions
  • Security Zone settings
  • Autocomplete information, including passwords
  • Cookies: persistent cookies are shared
  • HTML5 Storage: localStorage is shared

Not Shared

  • Binary add-ons: each only loads add-ons that are of the correct "bitness"
  • Cookies: session cookies are not shared
  • HTML5 Storage: sessionStorage is not shared

Q: Why does 64bit IE9 get faster JavaScript benchmark scores than IE8 (32 or 64) but slower scores than 32bit IE9?

In IE9 there's one other major difference between the 32bit and 64bit versions of IE. IE9 includes a new script interpreter which is much faster than the script interpreter in IE8. However, 32bit IE9 also includes a Just In Time (JIT) script compiler which converts script into machine code before running it. There is no JIT compiler for 64bit IE. So, for benchmarks like SunSpider (and script-heavy sites) 32bit IE9 runs script up to 4 times as fast as 64bit IE9 (which itself runs script around 5x as fast as IE8). So, you could end up paying a significant speed penalty when using 64bit IE9 vs using the default 32bit version.

Telemetry data shows that less than half of one percent of IE browsing sessions are conducted in the 64bit browser.

Note: IE10 Preview shipped a 64bit JavaScript JIT compiler, and the Windows 8 "Metro-style" browser (which will not load browser extensions) runs its tabs in 64bit processes.

Q: So, is there any benefit to using 64bit IE?

A: There are a few advantages to using the 64-bit version:

  • Security: DEP/NX is always on for 64bit processes. (Of course, on Vista SP1+, 32bit IE8+ has DEP/NX enabled by default too.)
  • Security: Memory protections like ASLR are more effective (because the address space is dramatically larger)
  • Security: Most bad guys only bother to write x86 shellcode, which will fail in an x64 process
  • It may crash less. (Because most addons don't load in 64bit IE, it tends to be more reliable.)
  • It may be faster to start up. (Because most addons aren't loaded. You can disable add-ons in 32bit IE if you'd like)

Q: Okay, so why offer 64bit IE at all? 

Because we have to.  :-) 

One thing to keep in mind is that Internet Explorer is basically the combination of a number of platform components, including the networking components (URLMon/WinINET), the rendering components (MSHTML), the script engines (JScript.dll/JScript9.dll, vbscript.dll) and a variety of other pieces that hold it all together. These components must be made available in 64bit versions so that 64bit applications can be built using these components.  Additionally, because Internet Explorer can be launched/created/used as a COM Server, we offer a 64bit version to enable hosting inside 64bit processes.

While we could have done work to make it harder for users to get to 64bit IE (e.g. by not creating a Start menu shortcut), I don't think there's any compelling reason to do so.

One day, 64bit IE might see a lot more use, as 64bit systems take over and 64bit add-ons become available.  Time will tell.

Got another question (or answer) about IEx64?  Let me know!

  • @Jack: There's no supported configuration that results in the behavior you describe. What is the "other program" in question?

  • Your initial posts were in 2009. Could you give a quick update re the status of IE 64 bit? Has anything much changed? And thank you by the way; this was great!

  • Alan: See

  • What an excellent Q&A!! I'd love it if every developer wrote in such detail about their software.

  • I still have not seen how people are removing the 64bit icon from All Programs. Anyone else mastered this yet?

  • Hi Eric We are using SCCM 2007 in our environment, We are using OSD to deploy all client machine they are having WIN 7 Enterprise SP1 64bit

    Recently we have started testing of Internet Explorer 9 , we are using IE9-Windows7-x64-enu /quiet /noupdate/ norestart command to update the Internet explorer. The upgrade are successful.. But we are facing some unique issue, when we see in ALL Programs we see two version of Internet Explorer

    1. Internet Explorer (x64)

    2. Internet Explorer

    by default the second is 32bit. But after the upgrade when we check we could see both internet explorer 9 with 64bit version...(both version are pointing to same exe).

    Before the upgrade we were having Ie8, which were pointing to correct exe's. We have checked it from help menu of internet explorer which shows 32bit and 64bit.

    I would like to know how we can see both version in ALL Programs. means both short cuts woulr point there respective exe's

  • I am using IE 64 bit and have a site in "Trusted site zone". The user agent is showing "WOW64". Is there any way to overwrite "WOW64" with "Win64" when site is in trusted site zone? Thanks in advance!

    EricLaw [ex-MSFT]: WOW64 means that the tab/content process is running as a 32bit process; Win64 means that it's running as a 64 bit process. Which version of IE / Windows are you using?

  • Windows 7, 64 bit system on Vaio. Surprisingly the Internet Explorer 8 64 bit is working but the the Internet Explorer 8 32 bit is not connecting to the internet. - it says 'address not valid'  

    EricLaw: The most likely explanation is that you have a 32bit browser extension which is buggy. Is there a change if you start IE in no-addons mode?

  • I have 2 problems that I am looking for help with.

    1- Facebook if I want to upload photos, I can only upload 5 at a time as I get a message that I am not currently using the latest adobe, and I have to download the latest version but even after doing this several times I still get the same message.

    2 I have a Scottish power home vend power pod which has worked fine for  about 2years, about 6 months ago my laptop installed some critical updates, then the power pod wouldn't work. After prerequisite checks, I get informed that my system doesn't support active x. I currently run  ie 11 on windows vista. If I do a system restore to prior the update it works fine and I don't have any problems on the desktop which runs Xp. I have tried adjusting all the settings to do with active x but nothing changes and scottish power won't help as the power pod works fine on the desktop it only happens when critical updates are installed.

  • I am using IE 10 on Win8. I set "Enable Enhanced Protected Mode" in Security Setting of IE 10. I confirm that IE is running 64 bit browser by I Run my applet, which load 64 bit DLLs from system. Receive Error Can't load AMD 64-bit.dll on a IA 32-bit platform Please Advise!

    [EricLaw] I'm not sure I understand your question, but enabling EPM doesn't turn on 64bit for all processes, only those in Protected Mode, and there are many other restrictions in EPM that would likely preclude a Java application from running properly in that mode.

  • Hi: I am running the 64-bit version of  WIndows Server 2012 R2 Foundation.

    I do see two versions of IE one under Program Files\Internet Explorer and one under Program Files(x86)\Internet Explorer. But no matter which version I run, the Help/About says the same thing; there is no reference to 64-bit. How can I determine if I am running the 64-bit version.

    [EricLaw] Read the IE10 post linked at the top of this one. As mentioned in that post, things are now much more complicated; typically, you will be running a 64bit frame and 32bit tabs.

    I also do not see an option to customize the tool bar (Right mouse clicking on the tool bar).

    [EricLaw] Right-click and tick the "Command bar" box. That's the only customizable bar.

  • @The Venkster - A hacky (but it works) way is to go to and see if it says "Win64" instead of "WOW64".

  • Is there a way to run only 32 bit instance of IE 10 in windows 2008 server? currently 64bit IE 10 i.e., iexplore.exe is running by default and if I change the TabProcGrowth key value from 0 to numeric, both 32 and 64 bit versions of IE10 are running. I want only 32bit version of IE 10, can you please suggest me a solution?

  • @Kumar-- You should read the post I link to in the very first line of this post. You can't do what you're asking.

  • Your suggestion of using alt H  to check the bitness version of IE 11 not only fails on ...

    [EricLaw] I suggest you re-read the first paragraph.

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