Add-ons: Detecting and Displaying Add-on Version Numbers

In the past months we worked with add-on developers to release new versions of their add-ons that follow IE’s guidelines and requirements for add-on development. We used the Upgrade Advisor to help update their users to the new versions. Some add-on vendors asked how IE determines and displays an add-on’s version. This post answers this question so that all add-on developers can design their versioning schemes to be compatible with IE features such as Manage Add-ons and the Upgrade Advisor.

There are two fields denoting the version of a binary file in Windows: file version and product version. Since IE add-ons are dynamic link library (DLL) files loaded into the browser, each add-on contains both of these version numbers. Here’s a screenshot of the properties dialog for one of our sample toolbars. Though the file version and product version are separate fields, they typically contain the same version string:

The file version and the product version of the Contoso Toolbar can be seen in the DLL file’s Properties window

IE displays the add-on DLL’s product version in Manage Add-ons. This is also the version that IE checks when determining whether the Upgrade Advisor dialog needs to be displayed for the add-on. IE looks directly into the DLL’s properties to extract the product version each time, and does not store the version in the registry. This design prevents incompatibilities when an add-on is auto-updated to a newer version.

We recommend add-on developers to update both version fields at the same time for consistency. It’s important to update the right version. For example, an error may result in the Upgrade Advisor dialog showing up for the wrong version of an add-on or the user believing that they have an older version of an add-on installed when looking at Manage Add-ons.

Thanks again to add-on developers for providing feedback and submitting questions. We wanted to answer this particular question as a blog post so that all developers have access to the information. We look forward to continue working with add-on developers in the coming months.

Herman Ng
Program Manager

Comments (21)
  1. confused says:

    Which spellchecker Add-on does MSFT recommend using since MSFT refuses to ship IE as a complete browser with one even though it is a highly required feature of a Web Browser.

  2. johnnyq3 says:


    I didn't know that a spell checker was a W3C standard that a browser must follow.  Altough I use iespell for my spell checking and it works so much better than a competitor's spell check.

  3. Michael says:

    Hello i need a question and fast will my computer be harmed a little at all if well since i got my computer in may should i have used Disk cleanup on windows 7 and click clean up old restore points? my computer was at 105GB free of 136GB.  now it says 112GB free of 136GB  does that mean i did my computer a favor? or no i did a stupid thing. i am a techy geek like person but i am still getting used to windows 7.

  4. Oreo says:

    hi i have a question what happend to My Web Slices 🙁 i don't see it in ie9 *CRIES*  is there going to be a addon in the new addon gallery for web slices in ie9 i want webslices back please!.

  5. West says:


    "The default IE9 doesn’t show web slices and visual search – but don’t be alarmed, they are still there and supported. And they are kept through your upgrade / install, and even uninstall.

    To see your web slices, just turn on the Favorites Bar (right-click on one of the chrome buttons). If you were to see a web slice on a site via in-page discovery, the green web slice icon would appear, you could install, and then the Favorites Bar is enabled."

  6. Mitch074 says:

    Eh, ok. Just one question: since (IE) extensions are DLLs, does it mean that an extension developer must compile a 32-bit x86 version, and a 64-bit x86-64 version? Can both cohabit?

    (I don't remember having trouble loading the same .xpi extension file on Firefox/Win32, Minefield/Win64, Firefox/Linux32, Firefox/Linux64 and Firefox/OSX, but then, they are not compiled code).

  7. Ooh says:

    @Mitch074: It means exactly that. And yes, they can cohabit since the registration is done in two different registry hives on a 64-bit Windows system.

  8. Xennan says:

    When will IE support Add-ons written in .NET? I think it is strange that it is still necessary to develop in C++ and old fashioned COM for an extension. It is like MSFT supports .Net halfheartedly. I expect Add-on development will get a boost when it is possible to use C# and VB.NET to create extension.

  9. Anonymous says:


    I'm not to familiar with either, but I thought that Silverlight was supposed to provide for .NET within IE.

  10. Mario says:

    =) I never thought there was Beauty in the web till Internet Explorer 9 showed up!! =D YES!! THERE IS BEAUTY IN THE WEB!!!!    Thanks Microsoft for making a better and safer webbrowser that i love to use!!! 😀

  11. ken says:

    I think they are intentionally keeping the barrier to entry very costly — both in terms of software but also in terms of ease-of-creation — so that hobbyists won't flood the market with addons. Instead, they come mostly from corps I believe. This allows them to try to ensure the maximum amount of security and robustness (efficiency) as they can.

    There's merits in both approaches I think, although I hope that MS realizes that most modern web developers wouldn't know the first thing about compiling a C++ app. But like I said, that could again me intentional in the hopes that addon devs will be experienced win32 devs and will therefore write code that plays better with the rest of the browser/os. On the other hand, it's MUCH more fun writing a full extension for competitor's browsers using Javascript in only an hour. I don't think I could even write a line of code in an hour if I were to try to make an IE addon…

  12. Drake says:


    Removing old System Restore points will not harm your computer.  System Restore allows you to revert how your system "looks" to points when certain records of how it looked (called "snapshots") in the past.  So, if you install a dodgy piece of software and can't remove it properly using Programs and Features in Control Panel then try taking your computer back to a record (snapshot) created before you installed it.  In Windows 7 it also provides a feature called "Previous Versions", which can help you get back a file you've accidentally deleted.

    Regularly cleaning up System Restore points therefore may reduce the benefit it may provide you if you did have a problem or find you've deleted a file.  But, if you're careful with your files and have not installed any new software in a while, then cleaning them up every so often won't do any harm.  May be worth noting though that if you go in System Properties you can limit how much disk space is used by the feature: easiest way to access it is to type "Create a restore point" into the Search box at the bottom of the Start menu, click the [Configure] for a drive then drag the slider.  Choose a reasonable limit then just forget about cleaning it up.

  13. JohnCz says:

    @West, something to consider as a possible replacement for RSS Headlines/Webslices in the Favorites Bar would be to enhance the pinned site capability to incorporate this.  Another avenue would be to create a toolbar for Windows Taskbar that provides preview of webslices and lists RSS headlines (think of it as an enhanced version of the Links toolbar).  Either solution would greatly minimize or eliminate the need for a Favorites Bar.

    Related to this is the lack of any visual cue indicating that webslices or rss feeds available on the page and conveniently list them.  Thats hidden in the Command Toolbar which is now disabled by default.  

    Hopefully your next Beta release will address these things.

  14. wow says:

    yes i am,

  15. JIM says:

    JPEG XR image



  16. Coolmario88cp says:

    Looks Like The Microsoft Crew Have Did Something that is as Amazing as Windows 7. By the way i love the themes!!!

  17. IE8 loyalist says:

    IE team, if you can completely eliminate any loss of functionality in the IE9 release even if it's "simplified", only then it will be considered a good release. You are merely swapping features in the beta. The version is a step ahead but it's a gamble, add some, lose some customization and features. This was not a problem with previous IEs. Something breaks and you either drop it due to lack of time or you purposefully dumb down it so much that all user customization is lost. Or features get lost in the redesign or overhaul which is again a shame. Fix that and IE9 will become a solid release.

  18. petter103 says:

    The addon- disable toast is nice but does not understand that delays may be caused by other things such as boot process not really finished and me eagerly launching IE9.

    Also, please consider adding search in favourites (basic search is OK, even better if you do it with intellisense). Very useful, and how hard can it be compared with all the other good stuff you guys did?

  19. Jimmy says:


    Well in the wikipedia article you linked…

    "Support for the format is available in Windows Imaging Component, .NET Framework (3.0 or newer), Windows Vista/Windows 7, _Internet Explorer 9_, and a number of other products"

    Looks like you got what you wanted already.

  20. johnnyq3 says:


    It looks like MS actually has a patent for HD photo.  So of course they support it in IE9.

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