Hello,

We have recently had an issue with Safari appending a ".txt" extension to downloaded files on our Umbraco site. We managed to find a solution and were encouraged to add it to the forum by Umbraco support, so here it is:

The problem: Safari is appending ".txt" extension to all downloads of unknown format. In our case, we had files with ".asc" extenstion and the resulting file was renamed to "filename.asc.txt".

The solution: As it turns out, Safari adds this extension based on the mime type in the Content-Type HTTP header. In our case, the Content-Type for .asc files was always text/plain, causing Safari to interpret the file as a ".txt". The solution was to add the following rewrite rules to the IIS Web.config:

<rewrite>
      <outboundRules>
        <rule name="Force .asc files mime type" enabled="true">
            <match serverVariable="RESPONSE_Content_Type" pattern=".*" />
            <conditions>
                <add input="{PATH_INFO}" pattern=".*asc"/>
            </conditions>
            <action type="Rewrite" value="application/octet-stream" />
        </rule>  
        <rule name="Enable content disposition" enabled="true">
            <match serverVariable="RESPONSE_Content_Disposition" pattern=".*" />
            <conditions>
                <add input="{PATH_INFO}" pattern=".*asc"/>
            </conditions>
            <action type="Rewrite" value="attachment" />
        </rule>
    </outboundRules>
</rewrite>

The first rule changes the mime type of ".asc" files to "application/octet-stream" which forces Safari to interpret it as a binary file and thus not rename it. The second rule adds a Content-Disposition header which tells browsers that the file should be downloaded rather than viewed in the browser.

Hope this will help someone in the future!