thoop

<?xml version="1.0"?>
<configuration>
    <system.webServer>
        <rewrite>
            <rules>
                <!--# Only proxy the request to Prerender if it's a request for HTML-->
                <rule name="Prerender" stopProcessing="true">
                    <serverVariables>
                        <set name="HTTP_X_PRERENDER_TOKEN" value="[...your token...]" />
                    </serverVariables>