Markdown to HTML

How to Use the Markdown to HTML Converter

1. Paste or type Markdown into the input pane. A README, a blog post draft, a Notion export, a GitHub wiki page, or any CommonMark-compatible text works.
2. Toggle between tabs: HTML Code shows the raw generated markup; Preview shows how that markup renders in the browser.
3. Click Copy HTML to paste the generated markup into a CMS, an email template builder, or an HTML file directly.
4. Iterate live - typing in the input pane updates both views on every keystroke so you can see exactly how your Markdown maps to HTML.

Under the Hood

The converter implements the commonly used core of CommonMark: headings, emphasis, lists, links, images, code blocks, blockquotes, and horizontal rules. It works line by line for block-level constructs (headings, list items, fences) and then passes the collected paragraph content through an inline parser that handles emphasis, backtick spans, links, and images. That two-pass architecture matches how every serious Markdown implementation (cmark, markdown-it, pulldown-cmark) structures its work.

For safety the converter escapes user HTML at the point of entry when it could form a <script> or other dangerous tag, rather than passing raw HTML through wholesale. The result is the same output you would get from a reasonable default CommonMark renderer: semantic HTML5 elements, no inline styles, no class names. Add styling by wrapping the output inside an existing design system - the Markdown-to-HTML step is intentionally style-agnostic. Recent patches also guard against malformed input like unbalanced image URLs that previously caused infinite loops.

Good Uses

• Writing an email in Markdown and converting to HTML for a Mailchimp or Brevo campaign that accepts custom HTML.
• Drafting a page in Markdown inside your editor and pasting HTML into a CMS that does not support Markdown directly.
• Producing a preview of a README change before pushing the commit, especially for GitHub-flavored features.
• Generating the HTML portion of a content file for a static site generator that does its own Markdown rendering but you want to compare output.
• Creating the inner HTML for a rich-text editor that accepts HTML as its serialisation format.
• Teaching Markdown syntax by letting students see source-to-HTML mapping in real time.

Watch Out For These

• GFM extensions. Task lists - [ ], tables with pipe syntax, and strikethrough with ~~text~~ are GitHub Flavored Markdown extensions. The core converter supports the most common ones; obscure extensions may not render.
• HTML inside Markdown. CommonMark allows raw HTML blocks. Those pass through the converter, which means they render in the preview. That is powerful but introduces XSS risk if the Markdown came from an untrusted source; keep the output sanitised if you accept input from users.
• Setext vs ATX headings. Underlined headings (=== under the text) are supported alongside #-style. Some older Markdown tools produce setext, so both shapes convert identically.
• Reference-style links. Links of the form [text][ref] followed by [ref]: url are recognised; the reference definition does not render as text.
• Hard line breaks. Two trailing spaces at the end of a line or a backslash produce a <br> per CommonMark. Single line breaks inside paragraphs are joined, which sometimes surprises people coming from platforms where every newline becomes a break.

CommonMark Specification

CommonMark is a standardised dialect of Markdown developed by John MacFarlane and others, first released in 2014 and currently at version 0.31.2. The spec at spec.commonmark.org includes a reference implementation (cmark) and a comprehensive test suite of over 600 cases. Before CommonMark, Markdown had dozens of incompatible implementations; the same input rendered differently on Reddit, Stack Overflow, GitHub, and Daring Fireball. CommonMark reduces that ambiguity. GitHub Flavored Markdown is specified as CommonMark plus a handful of extensions: tables, task lists, strikethrough, autolinks, and disallowed raw HTML. GFM is what you see on GitHub and is the closest thing to a "modern default" Markdown flavor.

Alternatives

markdown-it is the most popular JavaScript Markdown library and is what VS Code uses internally for its preview. remark is a full AST-based toolchain that lets you transform Markdown before rendering. pandoc, written in Haskell, is the Swiss Army knife: Markdown to HTML, to DOCX, to PDF, to LaTeX, all from one binary. For static site generators, Hugo ships with Goldmark, Astro uses remark internally, and Next.js supports MDX which combines Markdown with JSX. Reach for a build-step library when you need pipeline integration, custom plugins, or syntax highlighting. This in-browser tool is for the one-off case where you just need HTML from a Markdown snippet without installing anything.