What is Mermaid and why is it so popular?

Mermaid is a JavaScript-based diagramming language that uses text syntax to generate diagrams. It has become the de facto standard for diagrams in developer documentation, README files, and Markdown-based tools. Its popularity exploded further because AI models like Claude and ChatGPT frequently generate Mermaid syntax to illustrate architectures, workflows, and data models.

Does this viewer support Mermaid v10 and v11?

Yes. Zolkit's Mermaid viewer uses the latest stable version of mermaid.js (v11), which supports all current diagram types including flowcharts, sequence diagrams, class diagrams, ER diagrams, Gantt charts, state diagrams, mind maps, Git graphs, quadrant charts, timelines, and pie charts.

Can I preview diagrams generated by Claude or ChatGPT?

Absolutely — that's exactly what this tool is built for. When Claude, ChatGPT, Gemini, or any other AI assistant outputs Mermaid code (usually inside a code block), simply copy that code and paste it directly into this viewer. The diagram renders immediately with no extra steps.

What export formats are available?

You can export as SVG (scalable vector graphic — ideal for documentation, web pages, and anywhere you need crisp lines at any size) or as PNG (a 2× high-resolution raster image suitable for presentations, Word documents, and email). Both exports happen locally in your browser — no upload required.

Is there a code size limit?

There is no enforced size limit. In practice, very large diagrams (hundreds of nodes) may render slowly or produce visually cluttered output — this is a Mermaid limitation rather than a tool restriction. For best results, break complex diagrams into smaller focused diagrams.

Why isn't my diagram rendering?

The most common cause is a syntax error in the Mermaid code. Check that the diagram type keyword (flowchart, sequenceDiagram, classDiagram, etc.) is correct and on its own line. Special characters inside node labels may need to be quoted. The error panel below the preview shows the specific line causing the issue.

Mermaid Diagram Viewer

Paste any Mermaid code and see the diagram instantly. Export to SVG or PNG. Perfect for previewing AI-generated diagrams from Claude, ChatGPT, or Gemini.

Mermaid Code

Preview

Enter Mermaid code to preview your diagram

Diagram Types

Mermaid Flowchart Viewer Mermaid Sequence Diagram Viewer Mermaid Class Diagram Viewer Mermaid ER Diagram Viewer Mermaid Gantt Chart Viewer Mermaid State Diagram Viewer Mermaid Mind Map Viewer Mermaid Git Graph Viewer Mermaid Pie Chart Viewer Mermaid Timeline Diagram Viewer

Free Online Mermaid Diagram Viewer and Exporter

Zolkit's Mermaid Diagram Viewer lets you paste any Mermaid code and see a rendered diagram instantly — no installation, no sign-up, no server uploads. Everything runs in your browser, making it the fastest way to verify AI-generated diagrams from Claude, ChatGPT, or Gemini. Supports all major Mermaid diagram types: flowcharts, sequence diagrams, class diagrams, ER diagrams, Gantt charts, state diagrams, mind maps, Git graphs, pie charts, and timelines.

Instant Live Preview

Diagrams render automatically as you type, with a 300ms debounce so it never feels sluggish.

100% Private

All rendering happens in your browser using mermaid.js. Your code is never sent to any server.

Export SVG & PNG

Download your diagram as a crisp vector SVG or a high-resolution 2× PNG ready for docs and slides.

All Mermaid Diagram Types

Supports flowcharts, sequence diagrams, class diagrams, ER diagrams, Gantt charts, mind maps, Git graphs, and more.

AI Diagram Ready

Built for the AI era — directly preview diagrams generated by Claude, ChatGPT, Gemini, or any LLM.

Always Free

No account needed, no usage limits, no watermarks. Zolkit's Mermaid viewer is completely free forever.

How to Preview a Mermaid Diagram

1
Paste your Mermaid code into the editor on the left — you can copy it from an AI assistant or write it manually.
2
The diagram renders instantly in the preview panel on the right. If there's a syntax error, a message explains the issue.
3
Click 'Export SVG' or 'Export PNG' to download your diagram as a file ready for documentation, slides, or sharing.