Mermaid Free

Mermaid is a free text-to-diagram tool. You write a short block of Markdown-like code, and it renders a flowchart, sequence diagram, class or Gantt chart in the browser. It runs inside GitHub, Notion, Obsidian and most docs sites with no account needed.

What is Mermaid?

Mermaid is a JavaScript library from the open-source community (started by Knut Sveidqvist in 2014) that parses a text syntax called the Mermaid diagram language and draws SVG output. It is not a SaaS — you install it or paste code into a renderer, which is exactly why developers trust it. GitHub, GitLab, Jira and Azure DevOps all render Mermaid natively, so a diagram lives in the same pull request as the code it describes.

What can you draw with Mermaid?

• Flowcharts (graph TD / LR) for logic and pipelines.
• Sequence diagrams for API calls and auth flows.
• Class and ER diagrams for schemas and data models.
• Gantt charts for release plans.
• State, pie, journey and gitGraph types, plus mindmaps since v10.

Product Features

• MIT-licensed and free forever; the core npm package is ~100 KB gzipped.
• Renders to SVG, so diagrams stay sharp at any zoom level.
• Works offline in VS Code via the Markdown Preview Mermaid Support extension.
• Themeable with CSS variables and built-in themes (default, dark, forest, neutral, base).
• v11 (released 2024) added better layout, new diagrams and improved accessibility text.

Product Highlights

• Diagrams as code: text diffs in Git instead of binary image files.
• Zero lock-in: no vendor account, no per-seat fee, no export limit.
• Wide rendering support: GitHub, GitLab, Notion, Obsidian, Confluence and Docusaurus handle it out of the box.
• LLM friendly: ChatGPT and Claude write valid Mermaid syntax easily, which makes it a fast way to sketch architecture.

Use Cases

1. Documenting a CI/CD pipeline in a README.
2. Sketching a microservice request flow for a design review.
3. Drawing an ER diagram for a database migration PR.
4. Mapping a user signup funnel as a flowchart.
5. Drafting a sprint Gantt chart without a separate project tool.

Who should skip it?

Non-technical teams who want drag-and-drop editing will find the syntax annoying at first, and Mermaid’s automatic layout can crowd complex diagrams — you get limited manual control over edge routing. For polished marketing diagrams, a paid design tool still wins.

Quick Summary

• Mermaid is a free, MIT-licensed text-to-diagram library, not a paid service.
• It renders flowcharts, sequence, class, ER and Gantt diagrams from short code blocks.
• GitHub, GitLab, Notion and Obsidian render Mermaid with no extra setup.
• Best for developers who want version-controlled diagrams; weaker for pixel-perfect design work.