Markdown Preview

How the Markdown Preview tool works — real-time rendering with full GFM support.

Last updated: March 10, 2026 Try this tool

What It Does

The Markdown Preview tool provides a real-time side-by-side editor and renderer for Markdown. Write or paste Markdown on the left, see the rendered HTML on the right — updated live as you type. Full GitHub Flavored Markdown (GFM) support is included.

Key Features

  • Live preview — Rendered output updates as you type
  • GFM support — Tables, task lists, strikethrough, autolinks, and fenced code blocks
  • Split view — Side-by-side editor and preview panes
  • Syntax highlighting — Fenced code blocks are syntax-highlighted
  • Export options — Copy rendered HTML or download as an HTML file

Architecture

The tool uses marked, a fast Markdown parser and compiler. No WASM is required — pure JavaScript handles all rendering.

Processing Pipeline

  1. Input — User types or pastes Markdown in the editor pane.
  2. Parsing — On each keystroke (debounced), the Markdown is parsed by marked with GFM extensions enabled.
  3. Rendering — The parsed output is rendered as sanitized HTML in the preview pane.
  4. Highlighting — Code blocks are post-processed with syntax highlighting.

Code Structure

src/pages/tools/markdown-preview.astro   → Page with SEO
src/components/markdown-preview/
  MarkdownPreviewApp.tsx                → Main React component
src/lib/markdown.ts                     → marked configuration and rendering

Privacy & Security

All Markdown rendering happens locally in your browser. Your content is never sent to any server. The rendered HTML is sanitized to prevent XSS attacks from malicious Markdown input.

Technical Details

  • No WASM required — Pure JavaScript rendering
  • Parser: marked (~35KB gzipped) with GFM extension
  • Supported syntax: CommonMark + GitHub Flavored Markdown (tables, task lists, strikethrough, autolinks)
  • Rendering: Debounced live updates for smooth typing
  • Browser support: All modern browsers

FAQs

What Markdown flavor is supported?

The tool supports CommonMark with GitHub Flavored Markdown (GFM) extensions. This includes tables, task lists with checkboxes, strikethrough text, autolinks, and fenced code blocks with language-specific syntax highlighting.

Can I use this for README files?

Yes — the GFM support means this tool renders Markdown the same way GitHub does, making it ideal for previewing README.md files before committing.

Does it support LaTeX/math?

Not currently. LaTeX math rendering (KaTeX or MathJax) is planned for a future update.