Raw HTML omitted: your HTML disappears from Markdown

You put a <div>, an <iframe> or a <details> block in a Markdown file. The page builds fine – and the HTML is gone. In the output there’s a comment where your markup should be:

<!-- raw HTML omitted -->

And in the build log:

WARN  Raw HTML omitted while rendering "/content/about.md";
      see https://gohugo.io/getting-started/configuration-markup/#rendererunsafe

Why

Hugo renders Markdown with Goldmark, and Goldmark refuses to pass raw HTML through by default. It’s a safety default: if your Markdown comes from somewhere you don’t control, letting it emit arbitrary HTML – <script> included – is a hole. Hugo would rather drop it than trust it.

Your own content isn’t untrusted input, so for most sites this default is just in the way.

Fix 1: allow it

[markup.goldmark.renderer]
  unsafe = true

Your HTML now renders exactly as written. “Unsafe” is Goldmark’s word, not a warning about your site: it means HTML is passed through unchecked. If you write all the content yourself, that’s precisely what you want. If you render Markdown submitted by other people, it’s exactly what you don’t.

Fix 2: use a shortcode instead

If you’d rather keep the default, wrap the markup in a shortcode. layouts/_shortcodes/video.html:

<div class="video">
  <iframe src="https://player.vimeo.com/video/{{ .Get 0 }}" allowfullscreen></iframe>
</div>

and in the content file:

{{< video 123456 >}}

Templates are always allowed to emit HTML – only Markdown is restricted. This keeps the safety net and gives you markup you can reuse.

What silencing the warning does not do

Hugo helpfully suggests this in the log:

ignoreLogs = ['warning-goldmark-raw-html']

That hides the warning. It does not render your HTML – the <!-- raw HTML omitted --> comment stays exactly where it was. It’s the right setting when you’ve decided the omission is fine and you’re tired of the noise; it’s the wrong setting when you actually wanted the markup.

HugoKit’s preflight surfaces this warning before you publish, and its auto-fix adds the ignoreLogs line – the quiet option. If the HTML is meant to render, set unsafe = true in the config editor instead. See Preflight.