Tools

Mermaid Cheat Sheet — Diagram Syntax Reference

Mermaid draws diagrams from text in GitHub, GitLab, Notion, and most docs tools. This sheet covers the syntax for the diagram types you will use most.

Put it into practice with the matching tool.

Write a Mermaid diagram →

Flowchart

flowchart TDTop-down flowchart (LR, RL, BT for other directions)

A[Box] B(Rounded) C{Decision}Node shapes

D([Stadium]) E[(Database)] F((Circle))More node shapes

A --> BArrow

A -- yes --> B / A -->|yes| BArrow with a label

A -.-> B / A ==> BDotted / thick arrow

A --- BLine without an arrowhead

subgraph Name ... endGroup nodes in a box

classDef hot fill:#f96; class A hotDefine and apply a style class

Sequence diagram

sequenceDiagramStart a sequence diagram

participant A as BrowserDeclare a participant with an alias

A->>B: RequestSolid arrow message

B-->>A: ResponseDashed reply arrow

activate B / deactivate BShow an activation bar

Note over A,B: textNote spanning participants

alt ok ... else error ... endAlternative paths (also opt, loop, par)

ER diagram

erDiagramStart an entity-relationship diagram

USER ||--o{ ORDER : placesOne user places zero or more orders

|| |o }o }|Exactly one / zero or one / zero or more / one or more

USER { int id PK string email }Entity attributes with keys

Class and state diagrams

classDiagramStart a class diagram

Animal <|-- DogInheritance

class Dog { +bark() void }Class with a method

stateDiagram-v2Start a state diagram

[*] --> IdleInitial state

Idle --> Busy : startTransition with a label

Gantt and pie

gantt
  dateFormat YYYY-MM-DD

Start a Gantt chart

section BuildGroup tasks

Design :a1, 2026-11-01, 5dTask with an ID, start date, and duration

Code :after a1, 10dTask that starts after another

pie title Traffic
  "Search" : 60

Pie chart with labelled values

General

%% commentComment line

```mermaidFence that renders on GitHub and GitLab

A["Text with (brackets)"]Quote labels that contain special characters

Related guides

Diagrams as Code with Mermaid

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