Markdown Preview

About Markdown Preview

Markdown is the standard format for modern technical writing, used everywhere from GitHub READMEs and static site generators (like Hugo and Next.js) to personal knowledge bases (like Notion and Obsidian). However, writing raw Markdown without immediate visual feedback can be tedious, especially when formatting complex elements like tables, math equations, or diagrams. This professional-grade online Markdown editor solves that problem by providing a live, split-pane environment where you see the rendered output exactly as you type. Built for both quick edits and long-form writing, it features a distraction-free Zen Mode that hides all toolbars so you can focus entirely on your content. Unlike basic previewers, this tool includes advanced integrations typically only found in desktop IDEs. It natively supports the full CommonMark specification and GitHub Flavored Markdown (GFM), meaning your tables and task lists will render perfectly. For developers and researchers, it features intelligent code syntax highlighting for over 100 programming languages, high-performance KaTeX rendering for mathematical equations, and Mermaid.js support for building flowcharts and sequence diagrams directly from text. Once your document is complete, you can export the raw HTML, download the .md file, or generate a beautifully paginated PDF — all processed entirely locally in your browser for absolute privacy and zero server latency.

How to Use Markdown Preview

1. Write or Import Content: Begin typing in the left panel, paste existing Markdown, or click 'Import .md' to load a file from your device. The editor auto-saves your progress locally.
2. Format with Advanced Syntax: Use standard Markdown or try advanced features: wrap math in $ for KaTeX blocks, or use ```mermaid to generate dynamic diagrams.
3. Preview and Polish: Review the live rendered HTML on the right. Toggle the 'Split', 'Editor', and 'Preview' modes to maximize your workspace, or enter 'Zen Mode' for focused writing.
4. Export Your Document: Once finished, use the toolbar to 'Copy HTML' for your CMS, 'Download .md' to save the source, or 'Export PDF' for a formatted, paginated document.

Key Features

• Live Side-by-Side Preview: Watch your raw Markdown instantly transform into beautiful HTML on the right panel as you type on the left. Features synchronized scrolling so your code and preview are always perfectly aligned.
• KaTeX Math Equations: Write complex mathematical notation using LaTeX syntax. Supports both inline equations and full block equations rendered instantly via the high-performance KaTeX engine.
• Mermaid.js Diagrams: Create flowcharts, sequence diagrams, state diagrams, and Gantt charts using plain text. The integrated Mermaid parser generates crisp, scalable SVGs instantly.
• Distraction-Free Zen Mode: Click the Zen Mode toggle to hide all sidebars, navigation, and toolbars. The editor expands to fill your screen, creating an immersive, focused writing environment.
• Code Syntax Highlighting: Fenced code blocks automatically receive beautifully themed syntax highlighting. Simply append the language name (e.g., ```typescript or ```python) to your block.
• Paginated PDF Export: Generate professional, paginated PDF documents directly from your Markdown. The export engine prevents page breaks inside tables, images, and code blocks for a clean layout.
• GitHub Flavored Markdown (GFM): Fully supports standard CommonMark alongside GFM extensions, meaning pipe tables, strikethrough text, and task lists render exactly as they would on GitHub.
• 100% Private & Browser-Based: There is no backend server. Your text is processed entirely within your browser's JavaScript engine and auto-saved to local storage, ensuring complete data privacy.

Benefits

• Perfect GitHub READMEs: Stop making dozens of 'Update README' commits just to fix formatting. Test your tables, links, and code blocks here first to ensure they render perfectly.
• No Installation Required: Get IDE-level Markdown features (like Mermaid and KaTeX support) without installing heavy desktop applications, configuring VS Code plugins, or setting up Node environments.
• Instant CMS Content Creation: Write your blog posts or documentation naturally in Markdown, then use the 'Copy HTML' button to instantly grab clean, semantic HTML ready to paste into WordPress, HubSpot, or any CMS.
• Focus on the Content: With the auto-saving Zen Mode, you can draft technical specifications, essays, or notes without the visual clutter of standard word processors.
• Cross-Platform Compatibility: Write and preview Markdown seamlessly across Windows, Mac, Linux, and ChromeOS without relying on OS-specific markdown editors or desktop applications. It's universally accessible from any modern browser.
• Zero-Latency Real-Time Preview: Unlike server-side Markdown generators that require page reloads or API calls, our 100% client-side parser renders your text, KaTeX formulas, and Mermaid diagrams instantaneously as you type, ensuring an uninterrupted writing flow.

Supported Formats & Capabilities

• Input: Markdown text (.md, .markdown), KaTeX syntax, Mermaid syntax
• Output: Rendered HTML (Clipboard), Markdown (.md), PDF Document (.pdf)

Common Problems & Solutions

My KaTeX math equation isn't rendering properly.

Ensure you leave an empty line before opening your block equations ($). For inline math, wrap the equation in single dollar signs ($E=mc^2$). Avoid escaping backslashes manually inside the KaTeX blocks.

My Mermaid diagram shows a syntax error.

Ensure you are using the modern Mermaid syntax (e.g., 'flowchart TD' instead of the older 'graph TD;'). The editor uses the latest Mermaid.js engine which has stricter syntax validation.

My table isn't aligning correctly.

GFM tables require a separator row with dashes between the header and body (e.g., |---|---|). Ensure there is at least one dash per column. The parser will automatically format the output HTML.

The PDF export cut my code block in half.

The PDF export engine includes built-in CSS to avoid page breaks inside code blocks, tables, and images. However, exceptionally long code blocks may still force a break. Try splitting large code blocks or adding manual spacing.

Pro Tips & Best Practices

• Use the toolbar to quickly inject boilerplate syntax for headings, bold text, links, and code blocks.
• Click the 'Zen Mode' button (or press the floating toggle) when drafting long documents to eliminate visual distractions.
• Your content is automatically saved to your browser's Local Storage. If you accidentally close the tab, your text will be waiting for you when you return.
• When writing technical documentation, use the 'Copy HTML' feature to quickly port your styled Markdown into email newsletters or HTML-only platforms.

Privacy & Data Security

Total privacy is guaranteed. All Markdown parsing, HTML rendering, Mermaid compilation, and PDF generation are executed 100% locally on your device via JavaScript. Your documents are never uploaded to our servers, and auto-saves are stored securely in your browser's local cache.

Frequently Asked Questions

Does this editor support GitHub Flavored Markdown (GFM)?

Yes. The underlying parser fully supports GFM extensions, meaning your task lists, strikethroughs, and pipe tables will render exactly as they do on GitHub.

Can I use LaTeX math equations?

Absolutely. We have integrated the KaTeX engine. Use $ for inline math and $ for block math equations.

How do I create flowcharts and diagrams?

We support Mermaid.js natively. Simply create a fenced code block and specify 'mermaid' as the language identifier. The code block will automatically render as a scalable vector diagram.

Is the 'Export PDF' feature free?

Yes. Every tool on Run It Free, including high-quality paginated PDF generation, is completely free with no watermarks and no usage limits.

Are my documents saved online?

No. To protect your privacy, your Markdown content is never uploaded to any server. It is temporarily saved in your local browser storage so you don't lose work if you refresh the page.

Does syntax highlighting support my programming language?

We use Highlight.js, which automatically detects and colors over 100 different programming and markup languages within your fenced code blocks.

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