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Flowcharts - Basic Syntax

Graph

This statement declares a new graph and the direction of the graph layout.

%% Example code
graph TD

This declares a graph oriented from top to bottom.

graph TD
    Start --> Stop

%% Example code
graph LR

This declares a graph oriented from left to right.

Possible directions are:

  • TB - top bottom

  • BT - bottom top

  • RL - right left

  • LR - left right

  • TD - same as TB

graph LR
    Start --> Stop

Nodes & shapes

A node (default)

graph LR
    id1

graph LR
    id

Note that 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.

graph LR
    id1[This is the text in the box]

graph LR
    id1[This is the text in the box]

A node with round edges

graph LR
    id1(This is the text in the box);

graph LR
    id1(This is the text in the box)

A node in the form of a circle

graph LR
    id1((This is the text in the circle));

graph LR
    id1((This is the text in the circle))

A node in an asymetric shape

graph LR
    id1>This is the text in the box]

graph LR
    id1>This is the text in the box]

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

A node (rhombus)

graph LR
    id1{This is the text in the box}

graph LR
    id1{This is the text in the box}

Links between nodes

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

A link with arrow head

graph LR
    A-->B

graph LR;
    A-->B

An open link

graph LR
    A --- B

graph LR;
    A --- B

Text on links

A-- This is the text --- B

or

A---|This is the text|B;

graph LR;
   A-- This is the text ---B

A link with arrow head and text

A-->|text|B

graph LR;
    A-->|text|B

or

A-- text -->B

graph LR;
    A-- text -->B

Dotted link

-.->

graph LR;
   A-.->B;

Dotted link with text

-. text .->

graph LR;
   A-. text .-> B

Thick link

==>

graph LR;
   A ==> B

Thick link with text

== text ==>

graph LR;
   A == text ==> B

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:

graph LR
    d1["This is the (text) in the box"]

graph LR
    id1["This is the (text) in the box"]

Entity codes to escape characters

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

The flowchart defined by the following code:

    graph LR
        A["A double quote:#quot;"] -->B["A dec char:#9829;"]

This would render to the diagram below:

    graph LR
        A["A double quote:#quot;"] -->B["A dec char:#9829;"]

Subgraphs

subgraph title
    graph definition
end

An example below:

%% Subgraph example
graph TB
        subgraph one
        a1-->a2
        end
        subgraph two
        b1-->b2
        end
        subgraph three
        c1-->c2
        end
        c1-->a2

graph TB
   c1-->a2
   subgraph one
   a1-->a2
   end
   subgraph two
   b1-->b2
   end
   subgraph three
   c1-->c2
   end

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.

click nodeId 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:

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

graph LR;
    A-->B;
    click A callback "Tooltip for a callback"
    click B "http://www.github.com" "This is a tooltip for a link"

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

graph LR;
    A-->B;
    click A callback "Tooltip"
    click B "http://www.github.com" "This is a link"

When integration mermaid using the mermaidAPI #mermaidapi the function that binds the events need to be run when the finished graph has been added to the page. This is described in the API usage section.

Styling and classes

Styling links

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. 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;

Styling a node

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

%% Example code
graph LR
    id1(Start)-->id2(Stop)
    style id1 fill:#f9f,stroke:#333,stroke-width:4px;
    style id2 fill:#ccf,stroke:#f66,stroke-width:2px,stroke-dasharray: 5, 5;

graph LR
    id1(Start)-->id2(Stop)
    style id1 fill:#f9f,stroke:#333,stroke-width:4px
    style id2 fill:#ccf,stroke:#f66,stroke-width:2px,stroke-dasharray: 5, 5

Classes

More convenient then 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;

Css classes

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

<style>
    .cssClass > rect{
        fill:#FF0000;
        stroke:#FFFF00;
        stroke-width:4px;
    }
</style>

Example definition

graph LR;
    A-->B[AAA<span>BBB</span>];
    B-->D;
    class A cssClass;

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. In order to do so, you need to add the fontawesome as described in the instructions at the fontawesome web site.

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

The example code below

graph TD
    B["fa:fa-twitter for peace"]
    B-->C[fa:fa-ban forbidden]
    B-->D(fa:fa-spinner);
    B-->E(A fa:fa-camera-retro perhaps?);

Would render the graph below:

graph TD
    B["fa:fa-twitter for peace"]
    B-->C[fa:fa-ban forbidden]
    B-->D(fa:fa-spinner);
    B-->E(A fa:fa-camera-retro perhaps?);

Graph declarations with spaces between vertices and link and without semicolon

  • 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 introduce 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.

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

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