IIS .webp file - add a MIME Type - HTTP error 404.3

In this post, I describe how to add support for a .webp file in IIS and ASP.NET to fix the error:

"HTTP Error 404.3 - Not Found

The page you are requesting cannot be served because of the extension configuration. If the page is a script, add a handler. If the file should be downloaded, add a MIME map."

Cause

This error occurs because I'm trying to access an image in WebP format on a site in IIS or ASP.NET which does not have the .webp MIME type added.

Resolution

ASP.NET

To resolve the error in ASP.NET, add the following to web.config:

        <system.webServer>
            <staticContent>                
                <mimeMap fileExtension=".webp" mimeType="image/webp" />
            </staticContent>
        </system.webServer>

IIS

To resolve the error in IIS Manager:

- Open IIS

- Go to your site then double click MIME Types:

- Press Add... under Actions in the top right:

- Enter .webp as the File name extension and image/webp as the MIME type:

The WebP image should now load successfully: