Mermaid Diagram Editor
Write Mermaid diagrams with live preview. Export as SVG or PNG.
About This Tool
The Mermaid Diagram Editor provides a split-pane environment for writing and previewing Mermaid diagrams in real time. Type your diagram code on the left and see the rendered output update live on the right. Supports all major Mermaid diagram types: flowcharts, sequence diagrams, Gantt charts, ER diagrams, class diagrams, pie charts, and more.
A template library provides starting points for each diagram type, so you don't have to memorize the syntax. Simply pick a template, customize it, and export the result as SVG or PNG. The SVG export produces clean, resolution-independent vector graphics perfect for documentation and presentations.
Error messages are displayed inline when the Mermaid parser detects syntax issues, making it easy to debug complex diagrams. The diagram theme can be toggled between dark and light independently of the site theme. Mermaid diagrams are widely used in <Link href={getLocalePath(locale, "/tools/markdown-preview")} className="text-primary underline underline-offset-2"
Markdown documents — test your diagram here, then paste the code into your README. For optimizing the exported SVG, use the <Link href={getLocalePath(locale, "/tools/svg-optimizer")} className="text-primary underline underline-offset-2"
SVG Optimizer .
All rendering happens client-side using the mermaid.js library. Your diagram code never leaves your browser. For other code formatting tasks, check out the <Link href={getLocalePath(locale, "/tools/graphql-formatter")} className="text-primary underline underline-offset-2"
GraphQL Formatter or the <Link href={getLocalePath(locale, "/tools/json-formatter")} className="text-primary underline underline-offset-2"
JSON Formatter .
How to Use
- Select a template from the dropdown to start with a pre-filled diagram, or type your own Mermaid code in the editor.
- The preview updates automatically as you type (debounced for performance).
- Toggle the diagram theme between dark and light using the theme button.
- Click SVG to download the diagram as a scalable vector graphic, or PNG for a raster image.
- If the syntax is invalid, an error message appears below the preview with details about the issue.
- Press Ctrl+Enter to force a re-render, or Ctrl+Shift+C to copy the SVG markup.
Popular Mermaid Diagram Examples
FAQ
Is my data safe?
Yes. All Mermaid rendering happens in your browser using the mermaid.js library. Your diagram code is never sent to any server.
What diagram types are supported?
The editor supports all Mermaid diagram types including flowcharts (graph TD/LR), sequence diagrams, Gantt charts, ER diagrams, class diagrams, pie charts, state diagrams, and more.
Can I export diagrams as images?
Yes. You can export as SVG (vector, ideal for embedding in docs) or PNG (raster, ideal for presentations). The SVG export preserves all styling and is resolution-independent.
Does the editor support dark mode?
Yes. You can toggle between dark and light themes for the rendered diagram. The editor UI follows your system/site theme preference.
What happens if my Mermaid syntax has errors?
The editor displays a clear error message below the preview area with details about the syntax issue. The last valid diagram remains visible while you fix the error.
Can I use Mermaid diagrams in Markdown?
Yes. Many Markdown renderers (GitHub, GitLab, Notion) support Mermaid code blocks natively. Write your diagram here, test the output, then paste the code into a ```mermaid code block in your Markdown file.
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