Workarround: IE11 changing download file extension to .zip

At ClipFlair Gallery, apart from opening a ClipFlair activity in ClipFlair Studio, downloading of an activity (.clipflair) file is also supported.

However, because the component serialization file format of ClipFlair Studio is XML plus media assets packed in .zip archive (with nesting allowed, where components and whole activities can be placed in other activities), Internet Explorer 11 (and probably other browsers too) was downloading .clipflair files as .zip (changing their file extension).

At first, I thought that occured because I was using MIME type “application/zip” at the IIS web server/site settings for that file extension. So then I tried to change it to “application/octet-stream” hoping that one would be treated as an “opaque” data stream.

However, eventually I ended up setting a custom MIME type “application/clipflair” for the file extension “.clipflair”, because even with “application/octet-stream” (as with the “application/zip” that I had before), IE11 was still saving the .clipflair file as .zip (obviously detecting the zip content in the download stream).

<?xml version=”1.0″?>
<configuration>

<system.webServer>

<directoryBrowse enabled=”true” showFlags=”Size, Extension”/>

<defaultDocument>
<files>
<clear/>
<add value=”index.html”/>
<add value=”Default.aspx”/>
<add value=”Default.html”/>
</files>
</defaultDocument>

<caching>
<profiles>
<add extension=”.log”
policy=”CacheUntilChange”
kernelCachePolicy=”CacheUntilChange”/>
</profiles>
</caching>

<staticContent>
<mimeMap fileExtension=”.log” mimeType=”text/plain”/>
<mimeMap fileExtension=”.clipflair” mimeType=”application/clipflair”/>
<mimeMap fileExtension=”.dzi” mimeType=”text/xml”/>
<mimeMap fileExtension=”.dzc” mimeType=”text/xml”/>
<mimeMap fileExtension=”.cxml” mimeType=”text/xml”/>
</staticContent>

</system.webServer>

<system.web>
<compilation debug=”true” targetFramework=”4.0.3″/>
</system.web>

</configuration>