Mermaid

Mermaid lets you write diagrams as text and renders them as visuals. Instead of dragging shapes around in a GUI tool like draw.io, you describe your diagram in a lightweight syntax, and Mermaid generates the image. That means diagrams live alongside your code, version-control cleanly, and update without hunting through a visual editor.

It's built for developers, technical writers, and teams who want diagrams embedded in documentation, READMEs, wikis, or markdown-based doc platforms. Many tools that handle technical documentation support Mermaid natively, so diagrams render inline without any extra setup.

The diagram types it supports cover a wide range:

• Flowcharts for process and decision logic
• Sequence diagrams for showing interactions between systems or actors
• Gantt charts for project timelines
• Class and entity-relationship diagrams for data modeling
• State diagrams, pie charts, quadrant charts, and more

The syntax is intentionally minimal. A few lines of text produce a clean, readable diagram. Because everything is plain text, diagrams fit naturally into pull requests, code reviews, and documentation pipelines.

Beyond the core library, Mermaid also offers a live editor and a collaborative platform at mermaid.ai, where teams can build and share diagrams together. The live editor is useful for prototyping a diagram before dropping the syntax into a doc or codebase.