eriksmartt.com/blog

Triggering a browser’s “Save As…” dialog using a custom Content-Type header

My previous post, “Passing JSON via the X-JSON HTTP header with Django and Prototype“, contained an example on writing custom HTTP headers from a Django-based web application. Continuing with that theme, here’s another header trick that I use in one of my apps to force the browser’s “Save As…” dialog box when viewing a particular URL.

The feature that I wanted was the ability to generate an XML file based on an HTTP GET request, but to have the browser open a “Save As…” dialog instead of attempting to render it (as would normally happen with XML in a modern browser.) The solution is to exploit the web browser behavior of not handling unknown mime types. A sample implementation (written in Python for the Django Web Framework) follows:

def save_as_xml(request):
    import datetime

    current_time = datetime.now()

    response = HttpResponse('PUT THE XML HERE')
    response['Content-Type'] = 'application/x-generated-xml-backup'
    response['Content-disposition'] = 'Attachment; filename=export.%s.xml' % (current_time.strftime("%Y-%m-%d"))

    return response

Setting the Content-Type header to a made-up type ensures that the browser will not attempt to render the file. The Content-disposition header provides the mechanism for suggesting the filename of the content to be saved on the viewer’s system. In this case, I’m using the standard `datetime` module to insert the date into the suggested filename.