mermaid

What is mermaid?

Mermaid is a JavaScript-based diagramming and charting tool that renders Markdown-inspired text definitions to create and dynamically modify diagrams. It is particularly useful for creating flowcharts, sequence diagrams, class diagrams, state diagrams, Gantt charts, and more.

What are mermaid's main functionalities?

Flowcharts

Mermaid allows you to create flowcharts using a simple syntax. The above code creates a flowchart with decision points and different paths.

```mermaid
flowchart TD
    A[Start] --> B{Is it?}
    B -->|Yes| C[OK]
    B -->|No| D[Not OK]
    C --> E[End]
    D --> E[End]
```

Sequence Diagrams

Sequence diagrams can be created to represent interactions between different participants over time. The code sample shows a simple interaction between Alice and Bob.

```mermaid
sequenceDiagram
    participant Alice
    participant Bob
    Alice->>Bob: Hello Bob, how are you?
    Bob-->>Alice: I am good thanks!
```

Gantt Charts

Mermaid supports Gantt charts for project planning and scheduling. The code sample demonstrates how to define tasks and their durations.

```mermaid
gantt
    title A Gantt Diagram
    dateFormat  YYYY-MM-DD
    section Section
    A task           :a1, 2023-01-01, 30d
    Another task     :after a1  , 20d
    section Another
    Task in sec      :2023-01-12  , 12d
    another task     : 24d
```

Class Diagrams

Class diagrams can be used to represent the structure of a system by showing its classes, attributes, and methods. The code sample shows a simple class diagram with inheritance.

```mermaid
classDiagram
    class Animal
    Animal : +String name
    Animal : +int age
    Animal : +void eat()
    Animal : +void sleep()
    class Dog
    Dog : +String breed
    Dog : +void bark()
    Animal <|-- Dog
```

State Diagrams

State diagrams represent the states of an object and transitions between those states. The code sample shows a simple state diagram with different states and transitions.

```mermaid
stateDiagram-v2
    [*] --> Still
    Still --> [*]
    Still --> Moving
    Moving --> Still
    Moving --> Crash
    Crash --> [*]
```

Other packages similar to mermaid

flowchart.js

Flowchart.js is a simple library to create flowcharts using JavaScript. It is less feature-rich compared to Mermaid but is easier to use for basic flowchart needs.

js-sequence-diagrams

js-sequence-diagrams is a library specifically for creating sequence diagrams. It offers a more focused approach to sequence diagrams but lacks the versatility of Mermaid.

chart.js

Chart.js is a popular library for creating various types of charts and graphs. While it does not support diagrams like flowcharts or sequence diagrams, it excels in creating data-driven charts.

d3

D3.js is a powerful library for creating complex and interactive data visualizations. It offers more flexibility and control compared to Mermaid but requires a steeper learning curve.

README

mermaid

Special note regarding version 8.2

In version 8.2 a security improvement was introduced. A securityLevel configuration was introduced which sets the level of trust to be used on the parsed diagrams.

• strict: (default) tags in text are encoded, click functionality is disabled
• loose: tags in text are allowed, click functionality is enabledClosed issues:

⚠️ Note : This changes the default behaviour of mermaid so that after upgrade to 8.2, if the securityLevel is not configured, tags in flowcharts are encoded as tags and clicking is prohibited.

If your application is taking responsibility for the diagram source security you can set the securityLevel accordingly. By doing this clicks and tags are again allowed.

    mermaidAPI.initialize({
        securityLevel: 'loose'
    });

🖖 Keep a steady pulse: mermaid needs more Collaborators #866

Generation of diagrams and flowcharts from text in a similar manner as markdown.

Ever wanted to simplify documentation and avoid heavy tools like Visio when explaining your code?

This is why mermaid was born, a simple markdown-like script language for generating charts from text via javascript.

Mermaid was nominated and won the JS Open Source Awards (2019) in the category The most exciting use of technology!!! Thanks to all involved, people committing pull requests, people answering questions and special thanks to Tyler Long who is helping me maintain the project.

Flowchart

graph TD;
    A-->B;
    A-->C;
    B-->D;
    C-->D;

Sequence diagram

sequenceDiagram
    participant Alice
    participant Bob
    Alice->>John: Hello John, how are you?
    loop Healthcheck
        John->>John: Fight against hypochondria
    end
    Note right of John: Rational thoughts <br/>prevail!
    John-->>Alice: Great!
    John->>Bob: How about you?
    Bob-->>John: Jolly good!

Gantt diagram

gantt
dateFormat  YYYY-MM-DD
title Adding GANTT diagram to mermaid
excludes weekdays 2014-01-10

section A section
Completed task            :done,    des1, 2014-01-06,2014-01-08
Active task               :active,  des2, 2014-01-09, 3d
Future task               :         des3, after des2, 5d
Future task2               :         des4, after des3, 5d

Class diagram - :exclamation: experimental

classDiagram
Class01 <|-- AveryLongClass : Cool
Class03 *-- Class04
Class05 o-- Class06
Class07 .. Class08
Class09 --> C2 : Where am i?
Class09 --* C3
Class09 --|> Class07
Class07 : equals()
Class07 : Object[] elementData
Class01 : size()
Class01 : int chimp
Class01 : int gorilla
Class08 <--> C2: Cool label

Git graph - :exclamation: experimental

gitGraph:
options
{
    "nodeSpacing": 150,
    "nodeRadius": 10
}
end
commit
branch newbranch
checkout newbranch
commit
commit
checkout master
commit
commit
merge newbranch

Installation

CDN

https://unpkg.com/mermaid@<version>/dist/

Replace <version> with expected version number.

Example: https://unpkg.com/mermaid@7.1.0/dist/

Node.js

yarn add mermaid

Documentation

https://mermaidjs.github.io

Sibling projects

• mermaid CLI
• mermaid live editor
• mermaid webpack demo
• mermaid Parcel demo

Request for assistance

Things are piling up and I have hard time keeping up. To remedy this it would be great if we could form a core team of developers to cooperate with the future development mermaid.

As part of this team you would get write access to the repository and would represent the project when answering questions and issues.

Together we could continue the work with things like:

• adding more types of diagrams like mindmaps, ert diagrams etc
• improving existing diagrams

Don't hesitate to contact me if you want to get involved.

For contributors

Setup

yarn install

Build

yarn build:watch

Lint

yarn lint

We use JavaScript Standard Style. We recommend you installing editor plugins so you can get real time lint result.

Test

yarn test

Manual test in browser:

open dist/index.html

Release

For those who have the permission to do so:

Update version number in package.json.

npm publish

Command above generates files into the dist folder and publishes them to npmjs.org.

Credits

Many thanks to the d3 and dagre-d3 projects for providing the graphical layout and drawing libraries!

Thanks also to the js-sequence-diagram project for usage of the grammar for the sequence diagrams. Thanks to Jessica Peter for inspiration and starting point for gantt rendering.

Mermaid was created by Knut Sveidqvist for easier documentation.

Tyler Long has became a collaborator since April 2017.

Here is the full list of the projects contributors.