Markdown to HTML for Developers — Browser, Pandoc, marked.js

You drafted a post in Markdown but the blog platform only accepts HTML. You want to drop a Markdown-formatted body into an email template. You are pulling Markdown content into a CMS WYSIWYG editor. All of these scenarios end at the same step: converting Markdown into HTML.

Pandoc or a build script can do this locally, but typing a command for every quick paste gets tedious, and many people would rather not paste internal drafts into a third-party online tool. This guide covers the relationship between Markdown and HTML, when the conversion shows up in practice, and how to do it directly in the browser.

Quick answer

Paste your Markdown into Markdown to HTML and press Run. The HTML appears instantly. Nothing to install, and the conversion runs entirely in the browser — your data never leaves your machine.

The output follows two specifications: CommonMark for the core syntax, and the GitHub Flavored Markdown spec for tables, task lists, strikethrough, and autolinks. For how the two differ, see CommonMark vs GFM.

How Markdown and HTML relate

Markdown is a lightweight markup language that prioritizes human readability while still expressing structure. HTML is the format browsers actually render, with tags wrapping each piece of content. The two map cleanly onto each other. This Markdown:

# Heading

This is a paragraph with **bold** and _italic_.

- Item 1
- Item 2

becomes this HTML:

<h1>Heading</h1>
<p>This is a paragraph with <strong>bold</strong> and <em>italic</em>.</p>
<ul>
  <li>Item 1</li>
  <li>Item 2</li>
</ul>

Markdown was designed with HTML output in mind, and the syntax-to-tag mapping is largely one-to-one.

When the conversion comes up

Blog and CMS platforms without Markdown support

WordPress's classic editor, several legacy CMSes, and many in-house publishing tools still expect HTML directly. Drafting in Markdown and converting on the way in is faster than fighting a WYSIWYG editor for layout consistency.

HTML email

Newsletter platforms accept HTML bodies. Writing the source in Markdown keeps the draft readable while still letting you ship final HTML into a template.

Static sites and docs pipelines

Some static site generators or documentation tools do not parse Markdown directly and expect pre-rendered HTML as part of the build step.

Convert with FormatArc

Markdown to HTML takes pasted Markdown and produces HTML. There is nothing to install.

Step 1: Open the tool

Go to Markdown to HTML.

Step 2: Paste your Markdown

Paste the Markdown source into the left pane. Headings, lists, links, images, fenced code blocks, and the rest of the common syntax are supported.

Step 3: Hit Run

Press Run and the HTML appears in the right pane.

GitHub Flavored Markdown is enabled, so pipe tables (| col1 | col2 |) and task list checkboxes (- [x]) are converted to the corresponding HTML elements.

The conversion runs entirely in the browser. Unpublished drafts and internal documents stay on your machine.

Supported syntax

The main GFM features are covered:

• Headings (# through ######)
• Paragraphs and line breaks
• Emphasis (**bold**, _italic_, ~~strikethrough~~)
• Ordered and unordered lists
• Task lists (- [ ], - [x])
• Links and images
• Inline code and fenced code blocks
• Tables
• Blockquotes
• Horizontal rules

Math notation (KaTeX, MathJax) is not supported.

For a deeper look at how Markdown tables are written — pipes, alignment, escaping cells, multi-line content — see the Markdown table syntax cheatsheet.

Markdown to HTML in code: when you need a library

A browser tool is great for one-off conversions, but if you are building a pipeline, a static site, or embedding conversion inside an app, a JavaScript library or CLI is the right fit. Here are the options most developers reach for.

marked.js (browser and Node)

A small, fast Markdown parser that runs in both the browser and Node. Install with npm install marked and convert in one line:

import { marked } from 'marked';

const html = marked.parse('# Hello\n\nThis is **bold**.');

GFM is enabled by default, so task lists, pipe tables, and fenced code blocks all follow the spec without extra setup.

markdown-it (extensible parser)

Another popular Markdown-to-HTML parser, built around a plugin system. Reach for it when you need footnotes, container blocks, custom containers, or any non-standard syntax:

import MarkdownIt from 'markdown-it';

const md = new MarkdownIt({ html: true, linkify: true });
const html = md.render('# Hello\n\nThis is **bold**.');

For tables and task lists, install the GFM-equivalent plugins (markdown-it-task-lists, etc.) since they are not enabled by default.

Pandoc (CLI)

The universal document converter. Best fit for build pipelines, batch jobs, or when you need to convert between formats outside Markdown ↔ HTML:

pandoc -f markdown -t html input.md -o output.html

Pandoc supports CommonMark, GFM, MultiMarkdown, and more via flags. Slower than JS libraries for a single conversion, but unmatched for format coverage and PDF / DOCX output.

Comparison

If you only need to paste Markdown and copy HTML, the browser tool above is enough. For automated builds, Pandoc. For app integration or shipping a parser in a frontend bundle, marked.js or markdown-it.

Things to watch when using the output

Sanitize untrusted input separately

Markdown allows raw HTML, which means any <script> tags in the source pass straight through to the output. If you are converting your own writing this is fine. If you are converting input from users or any untrusted source, run the result through DOMPurify or a similar sanitizer before rendering it.

No styling included

The output is structural HTML only. CSS is not added. The expectation is that wherever you paste it — a blog, a CMS, an email template — provides the visual styles.

Syntax highlighting in code blocks

Specifying a language with ```js adds class="language-js" to the rendered <code> element, but actual syntax highlighting requires loading something like Prism.js or highlight.js on the page that renders it.

Frequently asked questions

Does this support GitHub Flavored Markdown (tables, task lists, fenced code)?

Yes. The converter follows the GitHub Flavored Markdown spec, so pipe tables (| col1 | col2 |), task list checkboxes (- [x]), strikethrough (~~text~~), and fenced code blocks with optional language hints are all converted to the corresponding HTML elements.

Is the conversion done in the browser?

Yes. Both the parsing and HTML generation run entirely in your browser using JavaScript. Nothing is uploaded to a server, so internal drafts and unpublished documents stay on your machine.

Should I sanitize the HTML output before publishing?

If the source is your own writing, the output is safe to use directly. If the Markdown comes from an untrusted source such as form input or third-party content, pass the result through a sanitizer like DOMPurify before rendering it. Raw HTML embedded in Markdown — including <script> tags — passes through to the output as-is.

How is this different from Pandoc?

Pandoc is a powerful command-line converter that handles many formats and produces highly customizable output, but it requires installation and a terminal. This browser tool is faster for one-off conversions: paste, click Run, copy the result. For build pipelines and batch jobs, Pandoc is still the better fit.

Can I convert HTML back to Markdown?

Yes. For the reverse direction, use the HTML to Markdown converter, which strips HTML tags down to clean Markdown source. The companion article is the HTML to Markdown guide.

Wrapping up

Converting Markdown to HTML is something every Markdown user runs into eventually. For one-off conversions, a browser tool like Markdown to HTML is faster than installing and remembering a CLI.

For the reverse direction, see HTML to Markdown. To turn CSV into a Markdown table, see the CSV to Markdown guide. If you want the same conversion from your browser toolbar, check the FormatArc Chrome Extension 2026 guide.