ttp://127.0.0.1:8080
</code></pre>
<p>Now, click on the main button on the simple UI. Since nothing is configured yet, the call should result in a &ldquo;failed to fetch&rdquo; error, and you should see the following error in your browser&rsquo;s developer tools:</p>
<pre><code>Access to fetch at &#39;http://cors.oto.tools:9999/&#39; from origin &#39;http://127.0.0.1:8080&#39; has been blocked by CORS policy: 
No &#39;Access-Control-Allow-Origin&#39; header is present on the requested resource. If an opaque