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  • Sergej Roswall Bogachov 1 post 71 karma points
    Apr 08, 2021 @ 11:17
    Sergej Roswall Bogachov

    Safari appending .txt to downloads


    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:

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

    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!

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