Configs2026年4月12日·1 分钟阅读

Mermaid — Generate Diagrams from Text Like Markdown

Mermaid is a JavaScript-based diagramming tool that renders Markdown-inspired text definitions to create diagrams and visualizations. Flowcharts, sequence diagrams, Gantt charts, class diagrams, ER diagrams, and more — all from plain text. Natively supported in GitHub Markdown.

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快速使用

先拿来用，再决定要不要深挖

这里应该同时让用户和 Agent 知道第一步该复制什么、安装什么、落到哪里。

In GitHub Markdown (natively supported):

```mermaid
flowchart TD
    A[User visits site] --> B{Logged in?}
    B -->|Yes| C[Dashboard]
    B -->|No| D[Login page]
    D --> E[Enter credentials]
    E --> B
```

Programmatic usage:

npm i mermaid
<script type="module">
  import mermaid from "https://cdn.jsdelivr.net/npm/mermaid@11/dist/mermaid.esm.min.mjs";
  mermaid.initialize({ startOnLoad: true, theme: "dark" });
</script>

<pre class="mermaid">
sequenceDiagram
    Client->>API: POST /login
    API->>DB: SELECT user
    DB-->>API: user record
    API-->>Client: JWT token
</pre>

CLI rendering:

npm i -g @mermaid-js/mermaid-cli
mmdc -i input.mmd -o output.svg -t dark
mmdc -i input.mmd -o output.png -w 1200
介绍

Mermaid is a JavaScript-based diagramming and charting tool that renders Markdown-inspired text definitions to create and modify diagrams dynamically. Created by Knut Sveidqvist. Natively supported in GitHub Markdown, GitLab, Notion, Obsidian, Docusaurus, and many other platforms. Lets developers create documentation diagrams without Figma or draw.io.

What Mermaid Does

  • Flowcharts — TD, LR, RL, BT directions
  • Sequence diagrams — actor interactions with arrows
  • Class diagrams — UML-style
  • State diagrams — state machine flows
  • ER diagrams — entity-relationship
  • Gantt charts — project timelines
  • Pie charts — data distribution
  • Git graphs — branch visualization
  • Mindmaps — hierarchical thinking
  • Timeline — chronological events
  • Quadrant charts — 2x2 matrices
  • Block diagrams — architecture views

Architecture

Pure JavaScript/TypeScript library. Parses Mermaid syntax → builds internal graph → renders to SVG via dagre (layout algorithm) and D3 (rendering). Can run in browser, Node.js, or CLI.

Self-Hosting

Client-side library, no backend.

Key Features

  • 15+ diagram types
  • GitHub Markdown native
  • Dark and light themes
  • CLI for CI/CD rendering
  • Customizable via directives
  • Live editor (mermaid.live)
  • Plugin for Docusaurus, Obsidian, Notion
  • SVG and PNG export
  • Accessible (ARIA labels)

Comparison

Tool Input Types Integration
Mermaid Text 15+ GitHub, GitLab, Notion
PlantUML Text 15+ Java-based
draw.io GUI Any Web, desktop
Excalidraw GUI Freeform Web
D2 Text 10+ CLI

常见问题 FAQ

Q: GitHub 里怎么用？ A: 直接在 Markdown 文件中写 ````mermaid` 代码块，GitHub 自动渲染。无需安装任何东西。

Q: 和 PlantUML 比？ A: Mermaid 纯 JS（浏览器原生），PlantUML 需要 Java 后端。Mermaid 语法更简洁，PlantUML 功能更完整（活动图更强）。

Q: 能定制样式吗？ A: 可以。用 %%{init: {"theme": "forest"}}%% 或 CSS class 绑定。也支持完全自定义 theme JSON。

来源与致谢 Sources

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