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Mermaid Diagram Viewer

Render Mermaid diagrams instantly — flowcharts, sequence diagrams, and more with SVG/PNG export

Mermaid Diagram Viewer

Supports: graph TD/LR, nodes [rect] (rounded) {diamond} ((circle)), edges --> --- -.->, |labels|, subgraphs
YesNoStartDecisionProcess AProcess BEnd
5 nodes5 edges

Last updated:

This tool is provided as-is for convenience. Output should be verified before use in any production or critical context.

For AI agents: how to call this tool

Machine-readable contract, endpoints and examples. Humans can ignore this section.

Best Path For Builders

Browser workflow

Runs instantly in the browser with private local processing and copy/export-ready output.

Browser Workflow

This tool is optimized for instant in-browser execution with local data handling. Run it here and copy/export the output directly.

/mermaid-viewer/

For automation planning, fetch the canonical contract at /api/tool/mermaid-viewer.json.

How to Use Mermaid Diagram Viewer

  1. 1

    Paste Mermaid diagram syntax

    Enter Mermaid syntax for flowcharts, sequence diagrams, class diagrams, state machines, or Gantt charts. Start simple (flowchart LR) and build up.

  2. 2

    See live preview instantly

    Your diagram renders in real-time as you type. Syntax errors are highlighted; fix them to see the diagram update.

  3. 3

    Edit and refine interactively

    Add nodes, connections, labels, and styling without switching tools. Use Mermaid syntax for styling (classDef, linkStyle) for polish.

  4. 4

    Export as PNG, SVG, or PDF

    Download your diagram in vector (SVG) for infinite scaling or raster (PNG) for embedding in docs. PDF export for presentations.

  5. 5

    Share diagrams and embed in docs

    Copy the Mermaid code to paste into GitHub markdown, Notion, or documentation. Works natively in many platforms for live-updating diagrams.

Frequently Asked Questions

What diagram types are supported?
The viewer supports Mermaid flowchart/graph diagrams (graph TD, graph LR) with standard node shapes, edges, and labels. This covers the most common Mermaid use cases.
Can I export diagrams as images?
Yes, export as SVG (vector, scalable, copyable) for use in documentation, presentations, or web pages. The SVG can be opened in any browser or vector editor.
Can I use this for GitHub README diagrams?
Yes, write and preview your Mermaid code here, then copy it into your README's ```mermaid code block. GitHub natively renders Mermaid diagrams in markdown.
Does it show syntax errors?
Yes, invalid Mermaid syntax shows descriptive error messages to help you fix the diagram code. Common issues like missing brackets or invalid edge syntax are caught.
Is this tool free and private?
Yes. Free to use. All diagram rendering happens in your browser. Your diagram code is not sent to external servers.