Markdown to HTML is the most-rendered conversion on the internet. Every time you read a Reddit post, view a GitHub README, open a Notion page, or scroll a Slack channel, software is converting Markdown to HTML in real time so your browser can render it. The conversion happens billions of times a day. The libraries that do it are some of the most battle-tested code on the open web.
That ubiquity creates a strange situation. The tooling for Markdown-to-HTML conversion is enormous, fragmented, and confusing for someone who just needs to do the conversion once. The right tool for a developer rendering Markdown a million times in a CMS is the wrong tool for a writer who just needs the HTML output for a single email.
This guide walks the three approaches that cover almost every real workflow, ranks them by use case, and explains the choices that change which tool is right for you. The fastest path for a one-off conversion is to paste the Markdown into Scrub-a-Doc and copy the HTML. The rest of this post covers when that is the right call and when a heavier tool earns its place.
Every Markdown-to-HTML converter does roughly the same thing: it reads Markdown, builds an in-memory representation called an Abstract Syntax Tree, and walks the tree to emit HTML. A # becomes an <h1>. An asterisk becomes <em>. A dash becomes <li> inside a <ul>. The CommonMark specification defines exactly how this mapping should work for the standard cases.
Where converters diverge is on the extensions. GitHub Flavored Markdown adds tables, task lists, autolinking, and strikethrough. Other variants add footnotes, definition lists, or attribute syntax. Pick a converter whose extension support matches what you actually use. Picking one with too few extensions costs you formatting; picking one with too many tempts you to use features that downstream systems will not render.
Most converters also let you pre-process or post-process the conversion. You can run a custom function before parsing (to fix non-standard Markdown) or after rendering (to inject classes, sanitize HTML, or rewrite links).
For a one-off conversion, a browser-based tool is the right choice. You paste or upload the Markdown, you copy the HTML, you ship it.
Scrub-a-Doc handles this workflow. You can paste Markdown directly or upload a .md file. The conversion runs client-side, so the content never leaves your browser. The HTML output preserves the structure and matches GitHub Flavored Markdown’s behavior, which is what most modern systems expect.
When this method falls short: rendering Markdown inside an application (where you need the conversion to run programmatically), edge-case Markdown that requires custom parsing rules, and very large documents.
For developers, two JavaScript libraries dominate.
Marked is the lightweight, fast option. It runs in Node and the browser. The minimal usage is a single function call:
js
const { marked } = require("marked");
const html = marked.parse("# Hello\n\nThis is **bold**.");Marked supports GitHub Flavored Markdown by default, including tables, fenced code blocks, autolinking, and strikethrough. The Marked documentation covers options for sanitization, custom rendering, and async tokenization.
markdown-it is the more configurable option. Its plugin ecosystem is larger and the parser is stricter about CommonMark compliance. If you need footnotes, definition lists, or other extensions beyond GFM, markdown-it has a plugin for it. The plugin list on npm covers the major extensions.
Both libraries are widely used in production. Marked is the default in many static-site generators because it is fast and minimal. markdown-it is the default in others because it is extensible. Pick based on whether you need raw speed or extensibility.
For Python, python-markdown and mistune play similar roles. For Go, Goldmark is the standard. For Rust, pulldown-cmark is the canonical implementation. Every modern language has a credible CommonMark parser.
Pandoc handles Markdown-to-HTML alongside its many other conversions. For batch jobs and conversions that need to integrate into a build pipeline, it is the right tool.
The basic command:
pandoc input.md -o output.htmlFor better results, specify the format and ask for a standalone document with a <head>:
pandoc input.md -f gfm -t html5 --standalone -o output.htmlPandoc’s user guide covers options for templates, syntax highlighting, math rendering, and custom CSS injection. For batch processing, a one-line shell script handles a folder of .md files:
for f in *.md; do pandoc "$f" -o "${f%.md}.html"; doneWhen this method makes sense: you process documents weekly or daily, you want the conversion scripted, or you need features (math, citations, custom templates) that browser tools and JS libraries do not provide.
HTML inside Markdown. CommonMark allows raw HTML inside Markdown documents. This is useful for structures Markdown cannot represent (custom classes, embedded media, complex layouts). Most converters preserve raw HTML by default. If you are rendering user-submitted Markdown on a public site, sanitize the HTML output to prevent injection attacks. DOMPurify is the standard sanitizer.
Math. Standard Markdown does not support math. Pandoc, KaTeX, and MathJax all add math rendering. Pick the one your downstream system understands.
Syntax highlighting. Markdown’s fenced code blocks identify the language of the code. The HTML output is plain <code> unless you run the result through a syntax highlighter. Prism and highlight.js are the two most common. Pandoc has built-in support via the --highlight-style flag.
Tables. Standard Markdown does not support tables. GFM and most other practical variants do. If your output is missing tables, you are using a converter without GFM support.
Footnotes and definition lists. Both are common Pandoc Markdown extensions. CommonMark does not define them. If you need them, use Pandoc or a markdown-it plugin.
The conventional advice is “pick a Markdown library.” That works for developers. Here is the part that helps everyone else.
The right tool depends on whether you are converting once or rendering continuously.
If you write a Markdown document and need the HTML once (for a one-time email, a single landing page, a paste into a CMS that does not accept Markdown), use a browser tool. The conversion takes seconds. You ship the output. The library question never comes up.
If you build a system that renders Markdown on every page load (a blog engine, a documentation site, a chat application), pick a library and embed it. The browser tool is the wrong tool for this job because every reader would have to run the conversion themselves.
If you publish a documentation site that renders Markdown once per build, use Pandoc or a static-site generator. Hugo, Jekyll, Astro, and Docusaurus all run their own Markdown-to-HTML conversion at build time and ship pre-rendered HTML to readers.
These three modes are different jobs with different tools. Most “should I use Marked or markdown-it” debates miss the prior question of which mode you are in.
For a one-off conversion, the browser cleaner. Scrub-a-Doc handles paste-in Markdown and .md file uploads, runs client-side, and produces clean HTML.
For continuous rendering inside an application, Marked for speed or markdown-it for configurability. Pick based on whether your priorities lean toward minimum latency or maximum control.
For a documentation site or any build-time conversion, Pandoc or a static-site generator built around Markdown.
The mistake is reaching for the developer toolchain when the writer tool would have done the job in twenty seconds. Match the tool to the mode, not to whatever you saw recommended on a developer blog.
What does your team actually do with HTML output: ship it once, render it on demand, or rebuild it on a schedule?