Markdown + Mermaid Workspace

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Preview

Free Online Markdown & Mermaid.js Workspace

A fast, privacy-first Markdown renderer with built-in Mermaid.js diagram support. Paste or type Markdown on the left and watch a live preview appear on the right. Rendering happens entirely in your browser using marked.js, Mermaid.js, and DOMPurify loaded from a CDN. No account, no tracking cookies, no advertisements. Optional sharing lets you save documents to the server with a token-based link. Use it to preview README.md files, draft documentation, sketch architecture with flowcharts, or check how GitHub will render your Markdown before you commit.

What it does

Markdown live preview — GitHub-flavored Markdown renders as you type, with headings, lists, tables, code blocks, links and images.
Mermaid.js diagrams — render graph, flowchart, sequenceDiagram, classDiagram, stateDiagram, erDiagram, gantt, journey, pie, mindmap and timeline diagrams inline inside Markdown code fences.
Auto-render — the preview updates automatically on every keystroke and on paste, with lightweight debouncing to keep typing smooth.
Upload .md files — drag a Markdown file onto the editor or use the Upload button to open local files.
Download .md files — export your edited Markdown with one click (or Ctrl/Cmd + S).
Resizable split panes — drag the divider to give the editor or the preview as much room as you need.
Mobile responsive — panes stack vertically on small screens so it stays usable on a phone.
Secure by design — all HTML output is sanitized with DOMPurify to block XSS.
Optional sharing — click Share to upload your Markdown to the server and get a shareable link with a random token. No account needed. Documents auto-expire after a configurable retention period (default 15 days). Anyone with the link can view and edit — don't store secrets.

Use cases

Preview a README.md before pushing to GitHub or GitLab.
Draft technical documentation with embedded Mermaid architecture and sequence diagrams.
Quickly check Markdown table syntax without spinning up a repo.
Convert Markdown notes into readable HTML for a quick glance.
Teach or learn Markdown and Mermaid syntax with instant visual feedback.
Prototype flowcharts, Gantt charts and ER diagrams directly in Markdown.

How to use Mermaid diagrams

Put a Mermaid diagram inside a fenced code block marked mermaid:

```mermaid
flowchart LR
    A[Markdown] -->|parsed| B(marked.js)
    B --> C{Mermaid block?}
    C -->|yes| D[Mermaid.js]
    C -->|no| E[HTML]
    D --> E
    E --> F((Live preview))
```

Supported diagram types include flowchart/graph, sequenceDiagram, classDiagram, stateDiagram, erDiagram, gantt, journey, pie, mindmap, timeline, gitGraph and C4Context.

Privacy & security

This tool renders Markdown entirely in your browser. The page loads three open-source libraries from a CDN (marked.js, Mermaid.js and DOMPurify). All rendering happens locally; the server never renders your Markdown. There are no tracking cookies, no analytics scripts, and no ads.

The Share feature is optional and explicitly initiated by you. When shared, the raw Markdown text is stored on the server under a random token. The server stores only raw text — rendering is always client-side. Shared documents auto-expire (default 15 days, configurable up to 365 days). The token is the key: anyone with the link can view, edit, or delete the document. Do not store secrets or sensitive data in shared documents.

Malicious Markdown can only affect the browser tab it is opened in; DOMPurify strips dangerous HTML before it reaches the preview.

Frequently asked questions

Is this Markdown renderer free?

Yes. It is 100% free, has no login, no paywall and no usage limits.

Does it store my Markdown?

Not by default. Without using Share, your Markdown lives only in your browser tab. Closing the tab discards it. If you use the Share feature, the raw Markdown is stored server-side with a random token. Shared documents auto-expire after the configured retention period (default 15 days). You can also delete them manually.

Does it use tracking cookies or analytics?

No. There are no tracking cookies, no analytics scripts and no advertising networks loaded. The only third-party requests are to a CDN for the three open-source rendering libraries.

Can I use Mermaid diagrams?

Yes. Wrap the diagram source in a fenced code block tagged mermaid (three backticks followed by the word mermaid) and it will render inline in the preview.

Which Markdown flavor is supported?

GitHub-Flavored Markdown (GFM) via marked.js: tables, task lists, strikethrough, fenced code blocks, autolinks and more.

Does it work offline?

Once the three CDN libraries have been cached by your browser, the page works offline for editing and rendering. The Share feature requires a network connection.

Is my data sent to a server?

Only if you click Share. All rendering happens locally in your browser. The Share feature sends your raw Markdown to the server so others can access it via the generated link.