Mermaid Diagram Editor

Mermaid is a JavaScript-based diagramming and charting language that uses text definitions to create diagrams dynamically. Instead of dragging shapes around in a visual editor, you write simple, human-readable markup that gets rendered into professional diagrams — flowcharts, sequence diagrams, class diagrams, ER diagrams, Gantt charts, and more.

Mermaid has become the standard for diagrams-as-code in technical documentation. It's natively supported by GitHub Markdown, GitLab, Notion, Obsidian, and dozens of other platforms. Developers use it to document system architectures, API flows, database schemas, and project timelines right alongside their code.

Our Mermaid diagram editor provides syntax highlighting, diagram templates, and a built-in cheat sheet to help you write Mermaid code faster. Use one of the 8 built-in templates as a starting point, edit the code with live syntax highlighting, and open your diagram directly in Mermaid Live for rendering — all without leaving your browser.

1. Choose a template — Select from Flowchart, Sequence Diagram, Class Diagram, State Diagram, ER Diagram, Gantt Chart, Pie Chart, or Git Graph to get started with working code.
2. Edit the code — Modify the Mermaid syntax in the editor. The syntax-highlighted preview updates in real-time showing keywords, arrows, brackets, and labels in distinct colors.
3. Use the cheat sheet — Switch to the Cheat Sheet tab for a quick reference on node shapes, arrow types, and syntax for each diagram type.
4. Preview your diagram — Click "Open in Mermaid Live" to render your diagram instantly in the official Mermaid editor with your code pre-loaded.
5. Copy and use — Copy your Mermaid code to paste into GitHub README files, documentation, Notion pages, or any Mermaid-compatible platform.

• 8 diagram templates — Pre-built templates for flowcharts, sequence diagrams, class diagrams, state diagrams, ER diagrams, Gantt charts, pie charts, and git graphs.
• Syntax highlighting — Color-coded keywords, arrows, brackets, strings, comments, and labels make Mermaid code easy to read and edit.
• Built-in cheat sheet — Quick reference cards for flowchart nodes and arrows, sequence diagram syntax, class relationships, state transitions, and ER notation.
• One-click Mermaid Live preview — Opens your code directly in mermaid.live with automatic code transfer for instant diagram rendering.
• Line and character counts — Real-time stats help you track diagram complexity as you work.
• 100% client-side — Your diagram code never leaves your browser. No server uploads, no tracking.

• GitHub documentation — Write Mermaid diagrams for README files, wikis, and issues. GitHub renders Mermaid natively in Markdown code blocks.
• System architecture diagrams — Create flowcharts and sequence diagrams to document microservice communication, API flows, and data pipelines.
• Database schema visualization — Use ER diagrams to map out entity relationships, cardinality, and table structures for database documentation.
• Project planning — Build Gantt charts to visualize project timelines, task dependencies, and milestones for sprint planning.
• Learning Mermaid syntax — Use templates and the cheat sheet to learn Mermaid diagram types without memorizing the syntax from scratch.