Frequently Asked Questions

What is MD Viewer?

MD Viewer is a free online Markdown editor and previewer with live rendering. It supports standard Markdown, GitHub Flavored Markdown (GFM), LaTeX math equations, Mermaid diagrams, ABC music notation, SMILES molecular structures, syntax highlighting for 200+ programming languages, and dark/light themes. No account or installation required — everything runs in your browser.

Is MD Viewer free to use?

Yes, completely free with no sign-up. All core features — editing, previewing, exporting, syntax highlighting, math, and diagrams — are available without any account or payment. The document sharing feature is also free.

What makes MD Viewer different from other Markdown editors?

MD Viewer combines features that typically require multiple tools into one browser-based application: live preview, LaTeX math (KaTeX), Mermaid diagrams, ABC music notation, SMILES molecular structures, 3D STL model preview, VexTab guitar tablature, and syntax highlighting for 200+ languages. Most alternatives either require accounts, lack advanced rendering, or charge for premium features.

What Markdown syntax is supported?

MD Viewer supports the full CommonMark specification plus GitHub Flavored Markdown extensions:

• Headings, bold, italic, strikethrough, and inline code
• Links, images, and autolinks
• Ordered and unordered lists, task lists
• Tables with column alignment
• Blockquotes and horizontal rules
• Fenced code blocks with syntax highlighting
• Footnotes and definition lists
• LaTeX math (inline and display)
• Mermaid diagrams
• ABC music notation
• SMILES molecular structures

How do I write LaTeX math equations?

Use single dollar signs for inline math ($E = mc^2$) and double dollar signs for display math ($$\int_0^1 x^2 dx$$). MD Viewer uses KaTeX for fast, accurate math rendering. See our LaTeX Math Guide for a complete reference of supported commands.

How do I create diagrams?

Use Mermaid syntax inside a fenced code block with the mermaid language identifier. Mermaid supports flowcharts, sequence diagrams, class diagrams, Gantt charts, ER diagrams, state diagrams, and pie charts. You can also use our dedicated Mermaid Editor for focused diagram creation. See our Mermaid Diagrams Guide for syntax details.

Can I use MD Viewer to preview GitHub READMEs?

Yes. MD Viewer supports GitHub Flavored Markdown including tables, task lists, strikethrough, alerts, footnotes, Mermaid diagrams, and LaTeX math. It's an excellent way to preview how your README.md will look on GitHub before committing. Note that GitHub-specific features like @mentions and issue auto-linking won't be interactive.

Can I open local Markdown files?

Yes. Drag and drop any .md, .markdown, .mdown, or .txt file directly onto the editor to open it. The file content loads into the editor — the original file on your computer is not modified.

How do I export my work?

MD Viewer offers several export options:

• Copy HTML — Copy the rendered HTML to your clipboard for pasting into blogs, emails, or CMS platforms
• Print/PDF — Use your browser's Print function (Ctrl/Cmd+P) to save as PDF
• Download .md — Save the raw Markdown as a file
• Share link — Generate a shareable URL for your document

Your content is also auto-saved in your browser's localStorage between sessions.

Is there a file size limit?

There is no hard limit for local editing and preview. Browser performance may slow with very large documents (100,000+ characters), especially with many diagrams or math equations. For shared documents, the limit is approximately 1 MB of Markdown content.

Is my content private?

Yes, by default. Everything you type stays in your browser's localStorage and is never sent to any server. Content is only transmitted when you explicitly click the Share button to generate a link. We do not read, analyze, or sell your content.

How does document sharing work?

When you click Share, your Markdown content is uploaded and stored securely with a unique URL. Anyone with that link can view the rendered document (read-only). Shared documents expire after 90 days. You cannot edit a previously shared document — make changes and generate a new link instead.

Can I delete a shared document?

Shared documents automatically expire after 90 days. If you need a document removed sooner, contact us at [email protected] with the share URL.

Does MD Viewer work offline?

Once loaded, the core editing and preview features work without an internet connection since all rendering happens client-side. However, the Share feature requires internet access. Some web fonts may not load offline.

What browsers are supported?

MD Viewer works in all modern browsers: Chrome, Firefox, Safari, Edge, and their mobile versions. JavaScript must be enabled. We recommend using the latest version of your preferred browser for the best experience.

Does MD Viewer work on mobile devices?

Yes. The interface is responsive and adapts to mobile screens. On smaller screens, the editor and preview switch between a tabbed view rather than side-by-side panels. Touch gestures are supported for resizing panels on tablets.

My content disappeared after clearing browser data. Can I recover it?

Unfortunately, no. Since content is stored in your browser's localStorage, clearing browser data (cache, cookies, site data) will erase your saved Markdown. We recommend downloading important documents as .md files or sharing them to create a backup via the share link.