The Mermaid Diagram Generator lets you write Mermaid diagram syntax and see the rendered diagram in real time in a side-by-side preview. Mermaid is a text-based diagramming language that generates flowcharts, sequence diagrams, class diagrams, Gantt charts, entity-relationship diagrams, pie charts, and more from plain text definitions. It is supported natively by GitHub and GitLab Markdown, Notion, Confluence, and many documentation tools. Writing diagrams as text rather than drawing them manually has several advantages: diagrams can be stored in version control, reviewed in pull requests, generated programmatically, and updated by editing text rather than rearranging shapes. This tool provides real-time rendering, a syntax reference panel, and multiple diagram examples to help you get started. Mermaid Diagram Generator is commonly used as a create diagrams without upload and a browser-based diagram creator, making it practical for everyday tasks without requiring any software installation. For complete results, Reading Time Calculator can estimate how long a text takes to read, Readability Score can measure the reading difficulty of written content, and Text to Handwriting can convert typed text to handwritten-style output.
Mermaid syntax is designed to be readable as text even without rendering. A simple flowchart looks like: graph TD; A[Start] --> B{Decision}; B -->|Yes| C[Action]; B -->|No| D[End]. The indentation and arrow notation makes the structure clear even in raw text form. Sequence diagrams use participant and actor declarations followed by arrows (->>, -->>) to show message flow between components, which is ideal for documenting API call sequences, authentication flows, and event-driven systems. Class diagrams support inheritance, composition, and interface implementation, which is useful for documenting object-oriented system designs. Gantt charts display project timelines with tasks and dependencies. Entity-relationship diagrams document database schemas. For technical documentation in GitHub repositories, Mermaid code blocks (triple backtick followed by "mermaid") render automatically in Markdown files, README files, and GitHub Wiki pages without any plugins. For Confluence, a dedicated Mermaid macro or the built-in Markdown renderer supports it. When embedding in web pages, the mermaid.js library (available from CDN) renders diagrams client-side from script tags with type="text/x-mermaid". This tool is particularly useful for previewing and iterating on diagram syntax before embedding it in documentation.