Markdown → HTML

Paste Markdown, copy the rendered HTML. Output is sanitized and safe to paste into any CMS or blog platform.

Markdown

# Welcome to md.tooljo.com

A fast, **100% client-side** markdown viewer. Your text never leaves
the browser — open DevTools → Network and verify.

## What works

- GFM (tables, task lists, strikethrough, fenced code)
- ~~Strikethrough~~ and **bold** and *italic* and `inline code`
- [Links](https://tooljo.com), images, blockquotes, footnotes

## Tables

| Feature | Status | Notes |
|---|---|---|
| Live preview | ✅ | as you type |
| URL-hash share | ✅ | click "Share" |
| Privacy | ✅ | nothing leaves your browser |

## Code

```js
function greet(name) {
  return `Hello, ${name}!`;
}
```

## Task list

- [x] Render markdown
- [x] Render tables
- [x] Render Mermaid diagrams
- [ ] Add KaTeX math (coming soon)

## Mermaid diagrams

Type a fenced ```mermaid block and the preview renders it as an SVG.
The library lazy-loads — it only fetches when there's a diagram to draw.

```mermaid
graph LR
  A[Markdown source] --> B(marked parses)
  B --> C{has mermaid blocks?}
  C -->|no| D[Plain HTML output]
  C -->|yes| E[Lazy-load mermaid]
  E --> F[Render SVG diagrams]
  F --> D
```

> Click "Share" below to copy a link that contains this whole document
> compressed into the URL fragment. No backend involved.

Rendered

Why convert client-side

Many "Markdown to HTML" sites upload your text to their server, run it through a parser there, and send the HTML back. That's a privacy and bandwidth tradeoff for nothing — every modern browser can run marked just fine, and the converter is ~30KB of JavaScript.

This tool does it in your browser. Open DevTools → Network and verify: no requests are sent while you convert.

What's included in the output

GFM features that get rendered:

Headings (# H1 through ###### H6)
Bold (**bold**) and italic (*italic*)
Strikethrough (~~text~~)
Lists (ordered, unordered, nested, task lists with checkboxes)
Tables (with alignment markers)
Fenced code blocks with language hints
Inline code (`code`)
Links and autolinks (https://example.com becomes a link)
Blockquotes (with nesting)
Images with alt text
Horizontal rules (---)
Line breaks (\n becomes <br>)

What gets sanitized

DOMPurify strips:

<script> tags
Event handlers (onclick, onload, etc.)
javascript: URLs
Other XSS-risky patterns per OWASP guidance

Embedded HTML that's safe (e.g. <details>, <sub>, <kbd>) passes through. Markdown supports raw HTML by spec; the sanitizer ensures it can't be weaponized.

Batch conversion (CLI alternatives)

For converting many files at once, use a command-line tool:

# marked (Node)
npm install -g marked
marked input.md > output.html

# pandoc (cross-platform, more features)
pandoc input.md -o output.html

# mdbook (Rust, great for docs)
mdbook build

# In your build pipeline (JavaScript)
import { marked } from "marked";
const html = marked.parse(markdown);

HTML structure

The "Download .html" button packages the output in a minimal, styled HTML document:

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width,initial-scale=1">
  <title>Markdown export</title>
  <style>/* GitHub-styled defaults */</style>
</head>
<body>
  <!-- your rendered markdown -->
</body>
</html>

Open the file in any browser, or share it as a self-contained doc. For paste-into-CMS use cases, prefer "Copy HTML" — that gives you just the inner content.

FAQ

What's the difference between this page and the main viewer?

Same engine — but this page defaults to the preview-only mode and frames the UX around 'I have markdown, give me HTML.' Click 'Source' to switch to split view.

What HTML do I get?

Clean GFM-rendered HTML. Standard tags only (<h1>, <p>, <table>, etc.) — no inline styles, no JavaScript, no framework-specific markup. Safe to paste into any CMS.

Is the HTML sanitized?

Yes. Output passes through DOMPurify — <script>, event handlers, and other risky patterns are stripped. The 'Copy HTML' button always gives you safe-to-render output.

What's the difference between 'Copy HTML' and 'Download .html'?

Copy HTML gives you the inner content only — the rendered tags without a wrapping document. Paste into your CMS, blog editor, etc. Download .html wraps it in a complete <html> document with default styling — open the file in any browser to view.

Can I batch-convert multiple files?

Not in the browser tool. For batch conversion, use marked or pandoc from the command line — see the code examples below.