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Flowcharts - Basic Syntax

All Flowcharts are composed of nodes, the geometric shapes and edges, the arrows or lines. The mermaid code defines the way that these nodes and edges are made and interact.

It can also accommodate different arrow types, multi directional arrows, and linking to and from subgraphs.

Important note: Do not type the word "end" as a Flowchart node. Capitalize all or any one the letters to keep the flowchart from breaking, i.e, "End" or "END". Or you can apply this workaround.

A node (default)

Code:
mermaid
---
title: Node
---
flowchart LR
    id
null

Note The id is what is displayed in the box.

A node with text

It is also possible to set text in the box that differs from the id. If this is done several times, it is the last text found for the node that will be used. Also if you define edges for the node later on, you can omit text definitions. The one previously defined will be used when rendering the box.

Code:
mermaid
---
title: Node with text
---
flowchart LR
    id1[This is the text in the box]
null

Graph

This statement declares the direction of the Flowchart.

This declares the flowchart is oriented from top to bottom (TD or TB).

Code:
mermaid
flowchart TD
    Start --> Stop
null

This declares the flowchart is oriented from left to right (LR).

Code:
mermaid
flowchart LR
    Start --> Stop
null

Flowchart Orientation

Possible FlowChart orientations are:

  • TB - top to bottom
  • TD - top-down/ same as top to bottom
  • BT - bottom to top
  • RL - right to left
  • LR - left to right

Node shapes

A node with round edges

Code:
mermaid
flowchart LR
    id1(This is the text in the box)
null

A stadium-shaped node

Code:
mermaid
flowchart LR
    id1([This is the text in the box])
null

A node in a subroutine shape

Code:
mermaid
flowchart LR
    id1[[This is the text in the box]]
null

A node in a cylindrical shape

Code:
mermaid
flowchart LR
    id1[(Database)]
null

A node in the form of a circle

Code:
mermaid
flowchart LR
    id1((This is the text in the circle))
null

A node in an asymmetric shape

Code:
mermaid
flowchart LR
    id1>This is the text in the box]
null

Currently only the shape above is possible and not its mirror. This might change with future releases.

A node (rhombus)

Code:
mermaid
flowchart LR
    id1{This is the text in the box}
null

A hexagon node

Code:

Code:
mermaid
flowchart LR
    id1{{This is the text in the box}}
null

Render:

Code:
mermaid
flowchart LR
    id1{{This is the text in the box}}
null

Parallelogram

Code:
mermaid
flowchart TD
    id1[/This is the text in the box/]
null

Parallelogram alt

Code:
mermaid
flowchart TD
    id1[\This is the text in the box\]
null

Trapezoid

Code:
mermaid
flowchart TD
    A[/Christmas\]
null

Trapezoid alt

Code:
mermaid
flowchart TD
    B[\Go shopping/]
null

Double circle

Code:
mermaid
flowchart TD
    id1(((This is the text in the circle)))
null

Nodes can be connected with links/edges. It is possible to have different types of links or attach a text string to a link.

Code:
mermaid
flowchart LR
    A-->B
null
Code:
mermaid
flowchart LR
    A --- B
null
Code:
mermaid
flowchart LR
    A-- This is the text! ---B
null

or

Code:
mermaid
flowchart LR
    A---|This is the text|B
null
Code:
mermaid
flowchart LR
    A-->|text|B
null

or

Code:
mermaid
flowchart LR
    A-- text -->B
null
Code:
mermaid
flowchart LR
   A-.->B;
null
Code:
mermaid
flowchart LR
   A-. text .-> B
null
Code:
mermaid
flowchart LR
   A ==> B
null
Code:
mermaid
flowchart LR
   A == text ==> B
null

It is possible declare many links in the same line as per below:

Code:
mermaid
flowchart LR
   A -- text --> B -- text2 --> C
null

It is also possible to declare multiple nodes links in the same line as per below:

Code:
mermaid
flowchart LR
   a --> b & c--> d
null

You can then describe dependencies in a very expressive way. Like the one-liner below:

Code:
mermaid
flowchart TB
    A & B--> C & D
null

If you describe the same diagram using the the basic syntax, it will take four lines. A word of warning, one could go overboard with this making the flowchart harder to read in markdown form. The Swedish word lagom comes to mind. It means, not too much and not too little. This goes for expressive syntaxes as well.

Code:
mermaid
flowchart TB
    A --> C
    A --> D
    B --> C
    B --> D
null

New arrow types

There are new types of arrows supported as per below:

Code:
mermaid
flowchart LR
    A --o B
    B --x C
null

Multi directional arrows

There is the possibility to use multidirectional arrows.

Code:
mermaid
flowchart LR
    A o--o B
    B <--> C
    C x--x D
null

Each node in the flowchart is ultimately assigned to a rank in the rendered graph, i.e. to a vertical or horizontal level (depending on the flowchart orientation), based on the nodes to which it is linked. By default, links can span any number of ranks, but you can ask for any link to be longer than the others by adding extra dashes in the link definition.

In the following example, two extra dashes are added in the link from node B to node E, so that it spans two more ranks than regular links:

Code:
mermaid
flowchart TD
    A[Start] --> B{Is it?}
    B -->|Yes| C[OK]
    C --> D[Rethink]
    D --> B
    B ---->|No| E[End]
null

Note Links may still be made longer than the requested number of ranks by the rendering engine to accommodate other requests.

When the link label is written in the middle of the link, the extra dashes must be added on the right side of the link. The following example is equivalent to the previous one:

Code:
mermaid
flowchart TD
    A[Start] --> B{Is it?}
    B -- Yes --> C[OK]
    C --> D[Rethink]
    D --> B
    B -- No ----> E[End]
null

For dotted or thick links, the characters to add are equals signs or dots, as summed up in the following table:

Length123
Normal------------
Normal with arrow-->--->---->
Thick============
Thick with arrow==>===>====>
Dotted-.--..--...-
Dotted with arrow-.->-..->-...->

Special characters that break syntax

It is possible to put text within quotes in order to render more troublesome characters. As in the example below:

Code:
mermaid
flowchart LR
    id1["This is the (text) in the box"]
null

Entity codes to escape characters

It is possible to escape characters using the syntax exemplified here.

Code:
mermaid
    flowchart LR
        A["A double quote:#quot;"] -->B["A dec char:#9829;"]
null

Numbers given are base 10, so # can be encoded as #35;. It is also supported to use HTML character names.

Subgraphs

subgraph title
    graph definition
end

An example below:

Code:
mermaid
flowchart TB
    c1-->a2
    subgraph one
    a1-->a2
    end
    subgraph two
    b1-->b2
    end
    subgraph three
    c1-->c2
    end
null

You can also set an explicit id for the subgraph.

Code:
mermaid
flowchart TB
    c1-->a2
    subgraph ide1 [one]
    a1-->a2
    end
null

flowcharts

With the graphtype flowchart it is also possible to set edges to and from subgraphs as in the flowchart below.

Code:
mermaid
flowchart TB
    c1-->a2
    subgraph one
    a1-->a2
    end
    subgraph two
    b1-->b2
    end
    subgraph three
    c1-->c2
    end
    one --> two
    three --> two
    two --> c2
null

Direction in subgraphs

With the graphtype flowcharts you can use the direction statement to set the direction which the subgraph will render like in this example.

Code:
mermaid
flowchart LR
  subgraph TOP
    direction TB
    subgraph B1
        direction RL
        i1 -->f1
    end
    subgraph B2
        direction BT
        i2 -->f2
    end
  end
  A --> TOP --> B
  B1 --> B2
null

Interaction

It is possible to bind a click event to a node, the click can lead to either a javascript callback or to a link which will be opened in a new browser tab. Note: This functionality is disabled when using securityLevel='strict' and enabled when using securityLevel='loose'.

click nodeId callback
click nodeId call callback()
  • nodeId is the id of the node
  • callback is the name of a javascript function defined on the page displaying the graph, the function will be called with the nodeId as parameter.

Examples of tooltip usage below:

html
<script>
  const callback = function () {
    alert('A callback was triggered');
  };
</script>

The tooltip text is surrounded in double quotes. The styles of the tooltip are set by the class .mermaidTooltip.

Code:
mermaid
flowchart LR
    A-->B
    B-->C
    C-->D
    click A callback "Tooltip for a callback"
    click B "https://www.github.com" "This is a tooltip for a link"
    click A call callback() "Tooltip for a callback"
    click B href "https://www.github.com" "This is a tooltip for a link"
null

Success The tooltip functionality and the ability to link to urls are available from version 0.5.2.

?> Due to limitations with how Docsify handles JavaScript callback functions, an alternate working demo for the above code can be viewed at this jsfiddle.

Links are opened in the same browser tab/window by default. It is possible to change this by adding a link target to the click definition (_self, _blank, _parent and _top are supported):

Code:
mermaid
flowchart LR
    A-->B
    B-->C
    C-->D
    D-->E
    click A "https://www.github.com" _blank
    click B "https://www.github.com" "Open this in a new tab" _blank
    click C href "https://www.github.com" _blank
    click D href "https://www.github.com" "Open this in a new tab" _blank
null

Beginner's tipβ€”a full example using interactive links in a html context:

html
<body>
  <pre class="mermaid">
    flowchart LR
        A-->B
        B-->C
        C-->D
        click A callback "Tooltip"
        click B "https://www.github.com" "This is a link"
        click C call callback() "Tooltip"
        click D href "https://www.github.com" "This is a link"
  </pre>

  <script>
    const callback = function () {
      alert('A callback was triggered');
    };
    const config = {
      startOnLoad: true,
      flowchart: { useMaxWidth: true, htmlLabels: true, curve: 'cardinal' },
      securityLevel: 'loose',
    };
    mermaid.initialize(config);
  </script>
</body>

Comments

Comments can be entered within a flow diagram, which will be ignored by the parser. Comments need to be on their own line, and must be prefaced with %% (double percent signs). Any text after the start of the comment to the next newline will be treated as a comment, including any flow syntax

Code:
mermaid
flowchart LR
%% this is a comment A -- text --> B{node}
   A -- text --> B -- text2 --> C
null

Styling and classes

It is possible to style links. For instance, you might want to style a link that is going backwards in the flow. As links have no ids in the same way as nodes, some other way of deciding what style the links should be attached to is required. Instead of ids, the order number of when the link was defined in the graph is used, or use default to apply to all links. In the example below the style defined in the linkStyle statement will belong to the fourth link in the graph:

linkStyle 3 stroke:#ff3,stroke-width:4px,color:red;

Styling line curves

It is possible to style the type of curve used for lines between items, if the default method does not meet your needs. Available curve styles include basis, bump, linear, monotoneX, monotoneY, natural, step, stepAfter, and stepBefore.

In this example, a left-to-right graph uses the stepBefore curve style:

%%{ init: { 'flowchart': { 'curve': 'stepBefore' } } }%%
graph LR

For a full list of available curves, including an explanation of custom curves, refer to the Shapes documentation in the d3-shape project.

Styling a node

It is possible to apply specific styles such as a thicker border or a different background color to a node.

Code:
mermaid
flowchart LR
    id1(Start)-->id2(Stop)
    style id1 fill:#f9f,stroke:#333,stroke-width:4px
    style id2 fill:#bbf,stroke:#f66,stroke-width:2px,color:#fff,stroke-dasharray: 5 5
null

Classes

More convenient than defining the style every time is to define a class of styles and attach this class to the nodes that should have a different look.

a class definition looks like the example below:

    classDef className fill:#f9f,stroke:#333,stroke-width:4px;

Attachment of a class to a node is done as per below:

    class nodeId1 className;

It is also possible to attach a class to a list of nodes in one statement:

    class nodeId1,nodeId2 className;

A shorter form of adding a class is to attach the classname to the node using the :::operator as per below:

Code:
mermaid
flowchart LR
    A:::someclass --> B
    classDef someclass fill:#f96
null

Css classes

It is also possible to predefine classes in css styles that can be applied from the graph definition as in the example below:

Example style

html
<style>
  .cssClass > rect {
    fill: #ff0000;
    stroke: #ffff00;
    stroke-width: 4px;
  }
</style>

Example definition

Code:
mermaid
flowchart LR
    A-->B[AAA<span>BBB</span>]
    B-->D
    class A cssClass
null

Default class

If a class is named default it will be assigned to all classes without specific class definitions.

    classDef default fill:#f9f,stroke:#333,stroke-width:4px;

Basic support for fontawesome

It is possible to add icons from fontawesome.

The icons are accessed via the syntax fa:#icon class name#.

Code:
mermaid
flowchart TD
    B["fab:fa-twitter for peace"]
    B-->C[fa:fa-ban forbidden]
    B-->D(fa:fa-spinner)
    B-->E(A fa:fa-camera-retro perhaps?)
null

?> Mermaid is now only compatible with Font Awesome versions 4 and 5. Check that you are using the correct version of Font Awesome.

  • In graph declarations, the statements also can now end without a semicolon. After release 0.2.16, ending a graph statement with semicolon is just optional. So the below graph declaration is also valid along with the old declarations of the graph.

  • A single space is allowed between vertices and the link. However there should not be any space between a vertex and its text and a link and its text. The old syntax of graph declaration will also work and hence this new feature is optional and is introduced to improve readability.

Below is the new declaration of the graph edges which is also valid along with the old declaration of the graph edges.

Code:
mermaid
flowchart LR
    A[Hard edge] -->|Link text| B(Round edge)
    B --> C{Decision}
    C -->|One| D[Result one]
    C -->|Two| E[Result two]
null

Configuration...

It is possible to adjust the width of the rendered flowchart.

This is done by defining mermaid.flowchartConfig or by the CLI to use a JSON file with the configuration. How to use the CLI is described in the mermaidCLI page. mermaid.flowchartConfig can be set to a JSON string with config parameters or the corresponding object.

javascript
mermaid.flowchartConfig = {
    width: 100%
}