Flowcharts - Basic Syntax

Graph

This statement declares the direction of the Flowchart.

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

graph TD
    Start --> Stop
graph TD Start --> Stop

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

graph LR
    Start --> Stop
graph LR Start --> Stop

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

Flowcharts

This renders a flowchart that allows for features such as: more arrow types, multi directional arrows, and linking to and from subgraphs.

Apart from the graph type, the syntax is the same. This is currently experimental but when the beta period is over, both the graph and flowchart keywords will render in the new way. This means it is ok to start beta testing flowcharts.

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.**

Nodes & shapes

A node (default)

graph LR
    id
graph LR id

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.

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

Node Shapes

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 stadium-shaped node

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

A node in a subroutine shape

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

A node in a cylindrical shape

graph LR
    id1[(Database)]
graph LR id1[(Database)]

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}

A hexagon node

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

Parallelogram

graph TD
    id1[/This is the text in the box/]
graph TD id1[/This is the text in the box/]

Parallelogram alt

graph TD
    id1[\This is the text in the box\]
graph TD id1[\This is the text in the box\]

Trapezoid

graph TD
    A[/Christmas\]
graph TD A[/Christmas\]

Trapezoid alt

graph TD
    B[\Go shopping/]
graph TD B[\Go shopping/]

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

graph LR
    A-->B
graph LR A-->B
graph LR
    A --- B
graph LR A --- B
graph LR
    A-- This is the text! ---B
graph LR A-- This is the text ---B

or

graph LR
    A---|This is the text|B
graph LR A---|This is the text|B
graph LR
    A-->|text|B
graph LR A-->|text|B

or

graph LR
    A-- text -->B
graph LR A-- text -->B
graph LR;
   A-.->B;
graph LR; A-.->B;
graph LR
   A-. text .-> B
graph LR A-. text .-> B
graph LR
   A ==> B
graph LR A ==> B
graph LR
   A == text ==> B
graph LR A == text ==> B

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

graph LR
   A -- text --> B -- text2 --> C
graph LR A -- text --> B -- text2 --> C

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

graph LR
   a --> b & c--> d
graph LR a --> b & c--> d

You can then describe dependencies in a very expressive way. Like the onliner below:

graph TB
    A & B--> C & D
graph TB A & B--> C & D

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 graph harder to read in markdown form. The Swedish word lagom comes to mind. It means, not to much and not to little. This goes for expressive syntaxes as well.

graph TB
    A --> C
    A --> D
    B --> C
    B --> D

Beta: New arrow types

When using flowchart instead of graph there is the are new types of arrows supported as per below:

flowchart LR
    A --o B
    B --x C
flowchart LR A --o B B --x C

Beta: Multi directional arrows

When using flowchart instead of graph there is the possibility to use multidirectional arrows.

flowchart LR
    A o--o B
    B <--> C
    C x--x D
flowchart LR A o--o B B <--> C C x--x D

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:

graph TD
    A[Start] --> B{Is it?};
    B -->|Yes| C[OK];
    C --> D[Rethink];
    D --> B;
    B ---->|No| E[End];
graph TD A[Start] --> B{Is it?}; B -->|Yes| C[OK]; C --> D[Rethink]; D --> B; B ---->|No| E[End];

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:

graph TD
    A[Start] --> B{Is it?};
    B -- Yes --> C[OK];
    C --> D[Rethink];
    D --> B;
    B -- No ----> E[End];
graph TD A[Start] --> B{Is it?}; B -->|Yes| C[OK]; C --> D[Rethink]; D --> B; B ---->|No| E[End];

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

Length 1 2 3
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:

graph LR
    id1["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.

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

Subgraphs

subgraph title
    graph definition
end

An example below:

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

You can also set an excplicit id for the subgraph.

graph TB
    c1-->a2
    subgraph ide1 [one]
    a1-->a2
    end
graph TB c1-->a2 subgraph id1 [one] a1-->a2 end

Beta: flowcharts

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

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
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

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
  • 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"

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):

graph LR;
    A-->B;
    B-->C;
    click A "http://www.github.com" _blank
    click B "http://www.github.com" "Open this in a new tab" _blank
graph LR; A-->B; B-->C; click A "http://www.github.com" _blank click B "http://www.github.com" "Open this in a new tab" _blank

Beginners tip, a full example using interactive links in a html context:

<body>
  <div class="mermaid">
    graph LR;
        A-->B;
        click A callback "Tooltip"
        click B "http://www.github.com" "This is a link"
  </div>

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

graph LR
%% this is a comment A -- text --> B{node}
   A -- text --> B -- text2 --> C

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. 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 a node

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

graph 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
graph 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

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;

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

graph LR
    A:::someclass --> B
    classDef someclass fill:#f96;
graph LR A:::someclass --> B classDef someclass fill:#f96;

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

<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;
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.

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

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 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?);
  • 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.

graph LR
    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]

Configuration…

Is it 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.

mermaid.flowchartConfig = {
    width: 100%
}