How to I add a MIME type for a single specific file without extension in IIS?

Question

I've been getting a lot of 404 notifications on the .well-known/traffic-advice location on my server. After doing some research it turns out the Chrome Privacy Preserving Prefetch Proxy tries to find instructions on prefetching content from the website.

I would like to add this file to give a proper response, but the file needs a specific MIME type: application/trafficadvice+json

In IIS it is easy to add a new MIME type for a specific extension, but in this case the 'traffic-advise' file has no extension. Also it's not advisable to specify a MIME type for all extension-less files.

How can I add the MIME type for this specific file in IIS (or web.config)?

Answer 1

As other solutions did not work for me, I used the following workaround to make it work:

1. Add an extension to the file (/.well-known/traffic-advice) so it becomes traffic-advice.tdjson
2. Add the MIME type for tdjson in web.config (or use IIS):

    <system.webServer>
      <staticContent>
        <mimeMap fileExtension=".tdjson" mimeType="application/trafficadvice+json" />
      </staticContent>
    </system.webServer>

3. Install the URl rewrite module (https://www.iis.net/downloads/microsoft/url-rewrite)
4. Add this rule to your Redirects.config file

    <rule name="wellknown trafficadvice" stopProcessing="true">
      <match url="^\.well-known\/traffic-advice$" ignoreCase="true" />
      <action type="Redirect" url="/.well-known/traffic-advice.tdjson" redirectType="Permanent" />
    </rule>

5. Done