title: Why is this HTML5 document invalid?
body: <p>I'm getting pretty confused about an error message I'm getting when I try to validate any simple HTML document without a meta encoding like this:</p>
  <pre><code>&lt;!DOCTYPE html&gt;
  &lt;html&gt;
  &lt;head&gt;
  &lt;title&gt;Test&lt;/title&gt;
  &lt;/head&gt;
  &lt;body&gt;Test&lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  <p><a href="http://validator.w3.org" rel="nofollow noreferrer">The W3C validator</a> reluctantly accepts the document as valid with just a few warnings when it is pasted into the direct input form, but when the document is uploaded or loaded by URI, validation fails with this error message</p>
  <blockquote>
  <p>The character encoding was not declared. Proceeding using
  windows-1252.</p>
  </blockquote>
  <p>There are two things I don't understand about this error:</p>
  <ul>
  <li>Why is a missing character encoding considered an error, when fallback rules exist?</li>
  <li>Why is the validator assuming <a href="https://en.wikipedia.org/wiki/Windows-1252" rel="nofollow noreferrer">Windows-1252</a> instead of UTF-8, like any browser would?</li>
  </ul>
  <p>What is the explanation for these two points?</p>