Raw HTML in Markdown — HTML Passthrough

Q: How does this Markdown syntax convert to HTML?

## Raw HTML in Markdown One of Markdown's design principles is that you can use raw HTML anywhere in a Markdown document. Most Markdown parsers pass HTML tags through directly to the output. ### Block-Level HTML Block-level HTML elements (like , , ) must be separated from surrounding content by blank lines: markdown A regular paragraph. This is raw HTML inside Markdown. Another paragraph. Converts to: html A regular paragr

Understand how raw HTML tags are passed through when converting Markdown to HTML. Learn which elements work, security considerations, and when to use raw HTML.

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Detailed Explanation

Raw HTML in Markdown

One of Markdown's design principles is that you can use raw HTML anywhere in a Markdown document. Most Markdown parsers pass HTML tags through directly to the output.

Block-Level HTML

Block-level HTML elements (like <div>, <table>, <section>) must be separated from surrounding content by blank lines:

A regular paragraph.

<div class="custom-box">
  <p>This is raw HTML inside Markdown.</p>
</div>

Another paragraph.

Converts to:

<p>A regular paragraph.</p>
<div class="custom-box">
  <p>This is raw HTML inside Markdown.</p>
</div>
<p>Another paragraph.</p>

Important: Markdown syntax is not processed inside block-level HTML elements. So **bold** inside a <div> will not be converted to <strong>.

Inline HTML

Inline HTML elements (like <span>, <abbr>, <mark>) can be used within Markdown text:

This word is <mark>highlighted</mark> and this has a <span style="color:red">red</span> color.

Unlike block-level HTML, Markdown syntax is processed around inline HTML elements.

Common Use Cases for Raw HTML

Custom attributes: Adding id, class, or style to elements
Complex tables: Using colspan, rowspan, and multi-line cells
Embedded media: <video>, <audio>, and <iframe> elements
Details/summary: Collapsible sections with <details> and <summary>
Definition lists: <dl>, <dt>, <dd> elements not supported in basic Markdown

Security Considerations

Many Markdown renderers sanitize HTML to prevent XSS attacks. Tags like <script>, <style>, and event handlers (onclick, onerror) are typically stripped. When building a Markdown-to-HTML pipeline, always consider whether raw HTML should be allowed, restricted, or fully sanitized.

Use Case

Raw HTML passthrough is used when Markdown syntax is insufficient — embedding videos, creating complex layouts, adding custom CSS classes, or using semantic HTML elements like <details>, <figure>, and <aside>. It bridges the gap between Markdown simplicity and HTML's full expressiveness.

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