Mermaid

mermaid.js.org

Markdown-like syntax for diagrams — flowcharts, sequence charts, and Gantt from text.

Overview

Mermaid is a JavaScript-based diagramming and charting tool that lets you create diagrams and visualizations using Markdown-inspired text definitions. It renders these text definitions dynamically into SVG charts and diagrams, making it easy to create and modify complex visualizations without needing specialized design tools.

The tool addresses the problem of documentation falling out of sync with development by enabling developers to create easily modifiable diagrams that can be integrated into production scripts and code. Mermaid supports a wide variety of diagram types including flowcharts, sequence diagrams, Gantt charts, class diagrams, entity relationship diagrams, user journey diagrams, and many more.

Mermaid won the 2019 JavaScript Open Source Award for "The Most Exciting Use of Technology" and is actively maintained by a growing community of contributors.

Key features

Multiple diagram types (flowchart, sequence, Gantt, class, ER, user journey, etc.)
Markdown-inspired text syntax
Live Editor for interactive creation
SVG rendering
CDN and npm deployment options
Sandbox security mode for user-generated content
Community integrations
CLI tool available

Pros

Easy to learn for those familiar with Markdown
Integrates into documentation and code workflows
Supports many diagram types out of the box
Open source and actively maintained
Can be embedded in web applications
Reduces documentation maintenance overhead

Cons

Security considerations for user-generated content
Some interactive features disabled in sandboxed mode
Learning curve for complex diagram types
Requires JavaScript runtime

Use this if

You need to create diagrams programmatically, want diagrams in version control, or prefer text-based diagram definitions that integrate with your development workflow.

Skip this if

You need advanced design customization, prefer GUI-based diagram creation, or require real-time collaborative editing features.

Best for

Creating flowcharts and diagrams in documentationDevelopers who want to embed diagrams in codeTechnical documentation and architecture visualizationNon-programmers using the Live EditorTeams needing version-controlled diagrams

Alternatives

PlantUMLGraphvizLucidchartDraw.ioExcalidraw

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