Microsoft has released the fourth preview of Internet Explorer 10. As is the case with previous Platform Previews, the release is aimed at developers: the new features are important to those creating rich, complex web applications, but will have less impact on web users.
However, even web developers might struggle to get too excited about the latest preview, because they probably won’t be able to run it: it only works on the Windows 8 preview release that Microsoft shipped at its BUILD conference in September.
CORS allows one application to expose its data to another application even when the same-origin policy would otherwise deny such access. This is useful for creating “mashup” applications that combine web services from multiple different providers.
Microsoft has positioned its Platform Previews as a way to let developers test and provide feedback on new features so that they can inform Microsoft of bugs, and guide the development of new specifications. The first two Platform Previews for Internet Explorer 10 were made available to users of Windows 7. This preview, however, is not. If you want to use it, you’ll have to use the Windows 8 Developer Preview.
The third preview was in the same position; Microsoft did not release a Windows 7 version of Platform Preview 3. Instead, the version of Internet Explorer that shipped with the Windows 8 Developer Preview was the third preview. Though Internet Explorer 10 will support Windows 7 when released, web developers wanting to test the software now will have to use an unsupported, not-even-beta operating system to do so. And while they can do so using a virtual machine, doing so will disable most or all of the hardware acceleration features found in the browser, making it a second-rate experience.
But as important as Metro-style applications are to Microsoft, the browser will still have a substantial user base on Windows 7, and the web developers of today are far more likely to be using Windows 7 than they are Windows 8. Regular non-Metro web applications still matter. Effectively excluding this group from the preview—the group most likely to have valuable feedback and insight—makes one wonder what the entire purpose of the scheme is.
This article originally appeared on Ars Technica, Wired’s sister site for in-depth technology news.