Flowcharts - Basic Syntax

Flowcharts are composed of nodes (geometric shapes) and edges (arrows or lines). The Mermaid code defines how nodes and edges are made and accommodates different arrow types, multi-directional arrows, and any linking to and from subgraphs.

warning
If you are using the word "end" in a Flowchart node, capitalize the entire word or any of the letters (e.g., "End" or "END"), or apply this [workaround](https://github.com/mermaid-js/mermaid/issues/1444#issuecomment-639528897). Typing "end" in all lowercase letters will break the Flowchart.

warning
If you are using the letter "o" or "x" as the first letter in a connecting Flowchart node, add a space before the letter or capitalize the letter (e.g., "dev--- ops", "dev---Ops").

Typing "A---oB" will create a [circle edge](#circle-edge-example).

Typing "A---xB" will create a [cross edge](#cross-edge-example).

A node (default)

mermaid-example
---
title: Node
---
flowchart LR
    id

note
The id is what is displayed in the box.

tip
Instead of `flowchart` one can also use `graph`.

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.

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

Unicode text

Use " to enclose the unicode text.

mermaid-example
flowchart LR
    id["This ❤ Unicode"]

Markdown formatting

Use double quotes and backticks "\ text \" to enclose the markdown text.

mermaid-example
---
config:
  flowchart:
    htmlLabels: false
---
flowchart LR
    markdown["`This **is** _Markdown_`"]
    newLines["`Line1
    Line 2
    Line 3`"]
    markdown --> newLines

Direction

This statement declares the direction of the Flowchart.

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

mermaid-example
flowchart TD
    Start --> Stop

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

mermaid-example
flowchart LR
    Start --> Stop

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

mermaid-example
flowchart LR
    id1(This is the text in the box)

A stadium-shaped node

mermaid-example
flowchart LR
    id1([This is the text in the box])

A node in a subroutine shape

mermaid-example
flowchart LR
    id1[[This is the text in the box]]

A node in a cylindrical shape

mermaid-example
flowchart LR
    id1[(Database)]

A node in the form of a circle

mermaid-example
flowchart LR
    id1((This is the text in the circle))

A node in an asymmetric shape

mermaid-example
flowchart 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)

mermaid-example
flowchart LR
    id1{This is the text in the box}

A hexagon node

mermaid-example
flowchart LR
    id1{{This is the text in the box}}

Parallelogram

mermaid-example
flowchart TD
    id1[/This is the text in the box/]

Parallelogram alt

mermaid-example
flowchart TD
    id1[\This is the text in the box\]

Trapezoid

mermaid-example
flowchart TD
    A[/Christmas\]

Trapezoid alt

mermaid-example
flowchart TD
    B[\Go shopping/]

Double circle

mermaid-example
flowchart TD
    id1(((This is the text in the circle)))

Expanded Node Shapes in Mermaid Flowcharts (v11.3.0+)

Mermaid introduces 30 new shapes to enhance the flexibility and precision of flowchart creation. These new shapes provide more options to represent processes, decisions, events, data storage visually, and other elements within your flowcharts, improving clarity and semantic meaning.

New Syntax for Shape Definition

Mermaid now supports a general syntax for defining shape types to accommodate the growing number of shapes. This syntax allows you to assign specific shapes to nodes using a clear and flexible format:

A@{ shape: rect }

This syntax creates a node A as a rectangle. It renders in the same way as A["A"], or A.

Complete List of New Shapes

Below is a comprehensive list of the newly introduced shapes and their corresponding semantic meanings, short names, and aliases:

<!--@include: virtual:shapesTable -->

Example Flowchart with New Shapes

Here’s an example flowchart that utilizes some of the newly introduced shapes:

mermaid-example
flowchart RL
    A@{ shape: manual-file, label: "File Handling"}
    B@{ shape: manual-input, label: "User Input"}
    C@{ shape: docs, label: "Multiple Documents"}
    D@{ shape: procs, label: "Process Automation"}
    E@{ shape: paper-tape, label: "Paper Records"}

Process

mermaid-example
flowchart TD
    A@{ shape: rect, label: "This is a process" }

Event

mermaid-example
flowchart TD
    A@{ shape: rounded, label: "This is an event" }

Terminal Point (Stadium)

mermaid-example
flowchart TD
    A@{ shape: stadium, label: "Terminal point" }

Subprocess

mermaid-example
flowchart TD
    A@{ shape: subproc, label: "This is a subprocess" }

Database (Cylinder)

mermaid-example
flowchart TD
    A@{ shape: cyl, label: "Database" }

Start (Circle)

mermaid-example
flowchart TD
    A@{ shape: circle, label: "Start" }

Odd

mermaid-example
flowchart TD
    A@{ shape: odd, label: "Odd shape" }

Decision (Diamond)

mermaid-example
flowchart TD
    A@{ shape: diamond, label: "Decision" }

Prepare Conditional (Hexagon)

mermaid-example
flowchart TD
    A@{ shape: hex, label: "Prepare conditional" }

Data Input/Output (Lean Right)

mermaid-example
flowchart TD
    A@{ shape: lean-r, label: "Input/Output" }

Data Input/Output (Lean Left)

mermaid-example
flowchart TD
    A@{ shape: lean-l, label: "Output/Input" }

Priority Action (Trapezoid Base Bottom)

mermaid-example
flowchart TD
    A@{ shape: trap-b, label: "Priority action" }

Manual Operation (Trapezoid Base Top)

mermaid-example
flowchart TD
    A@{ shape: trap-t, label: "Manual operation" }

Stop (Double Circle)

mermaid-example
flowchart TD
    A@{ shape: dbl-circ, label: "Stop" }

Text Block

mermaid-example
flowchart TD
    A@{ shape: text, label: "This is a text block" }

Card (Notched Rectangle)

mermaid-example
flowchart TD
    A@{ shape: notch-rect, label: "Card" }

Lined/Shaded Process

mermaid-example
flowchart TD
    A@{ shape: lin-rect, label: "Lined process" }

Start (Small Circle)

mermaid-example
flowchart TD
    A@{ shape: sm-circ, label: "Small start" }

Stop (Framed Circle)

mermaid-example
flowchart TD
    A@{ shape: framed-circle, label: "Stop" }

Fork/Join (Long Rectangle)

mermaid-example
flowchart TD
    A@{ shape: fork, label: "Fork or Join" }

Collate (Hourglass)

mermaid-example
flowchart TD
    A@{ shape: hourglass, label: "Collate" }

Comment (Curly Brace)

mermaid-example
flowchart TD
    A@{ shape: comment, label: "Comment" }

Comment Right (Curly Brace Right)

mermaid-example
flowchart TD
    A@{ shape: brace-r, label: "Comment" }

Comment with braces on both sides

mermaid-example
flowchart TD
    A@{ shape: braces, label: "Comment" }

Com Link (Lightning Bolt)

mermaid-example
flowchart TD
    A@{ shape: bolt, label: "Communication link" }

Document

mermaid-example
flowchart TD
    A@{ shape: doc, label: "Document" }

Delay (Half-Rounded Rectangle)

mermaid-example
flowchart TD
    A@{ shape: delay, label: "Delay" }

Direct Access Storage (Horizontal Cylinder)

mermaid-example
flowchart TD
    A@{ shape: das, label: "Direct access storage" }

Disk Storage (Lined Cylinder)

mermaid-example
flowchart TD
    A@{ shape: lin-cyl, label: "Disk storage" }

Display (Curved Trapezoid)

mermaid-example
flowchart TD
    A@{ shape: curv-trap, label: "Display" }

Divided Process (Divided Rectangle)

mermaid-example
flowchart TD
    A@{ shape: div-rect, label: "Divided process" }

Extract (Small Triangle)

mermaid-example
flowchart TD
    A@{ shape: tri, label: "Extract" }

Internal Storage (Window Pane)

mermaid-example
flowchart TD
    A@{ shape: win-pane, label: "Internal storage" }

Junction (Filled Circle)

mermaid-example
flowchart TD
    A@{ shape: f-circ, label: "Junction" }

Lined Document

mermaid-example
flowchart TD
    A@{ shape: lin-doc, label: "Lined document" }

Loop Limit (Notched Pentagon)

mermaid-example
flowchart TD
    A@{ shape: notch-pent, label: "Loop limit" }

Manual File (Flipped Triangle)

mermaid-example
flowchart TD
    A@{ shape: flip-tri, label: "Manual file" }

Manual Input (Sloped Rectangle)

mermaid-example
flowchart TD
    A@{ shape: sl-rect, label: "Manual input" }

Multi-Document (Stacked Document)

mermaid-example
flowchart TD
    A@{ shape: docs, label: "Multiple documents" }

Multi-Process (Stacked Rectangle)

mermaid-example
flowchart TD
    A@{ shape: processes, label: "Multiple processes" }

Paper Tape (Flag)

mermaid-example
flowchart TD
    A@{ shape: flag, label: "Paper tape" }

Stored Data (Bow Tie Rectangle)

mermaid-example
flowchart TD
    A@{ shape: bow-rect, label: "Stored data" }

Summary (Crossed Circle)

mermaid-example
flowchart TD
    A@{ shape: cross-circ, label: "Summary" }

Tagged Document

mermaid-example
flowchart TD
    A@{ shape: tag-doc, label: "Tagged document" }

Tagged Process (Tagged Rectangle)

mermaid-example
flowchart TD
    A@{ shape: tag-rect, label: "Tagged process" }

Special shapes in Mermaid Flowcharts (v11.3.0+)

Mermaid also introduces 2 special shapes to enhance your flowcharts: icon and image. These shapes allow you to include icons and images directly within your flowcharts, providing more visual context and clarity.

Icon Shape

You can use the icon shape to include an icon in your flowchart. To use icons, you need to register the icon pack first. Follow the instructions to add custom icons. The syntax for defining an icon shape is as follows:

mermaid-example
flowchart TD
    A@{ icon: "fa:user", form: "square", label: "User Icon", pos: "t", h: 60 }

Parameters

• icon: The name of the icon from the registered icon pack.
• form: Specifies the background shape of the icon. If not defined there will be no background to icon. Options include:
• square
• circle
• rounded
• label: The text label associated with the icon. This can be any string. If not defined, no label will be displayed.
• pos: The position of the label. If not defined label will default to bottom of icon. Possible values are:
• t
• b
• h: The height of the icon. If not defined this will default to 48 which is minimum.

Image Shape

You can use the image shape to include an image in your flowchart. The syntax for defining an image shape is as follows:

flowchart TD
    A@{ img: "https://example.com/image.png", label: "Image Label", pos: "t", w: 60, h: 60, constraint: "off" }

Parameters

• img: The URL of the image to be displayed.
• label: The text label associated with the image. This can be any string. If not defined, no label will be displayed.
• pos: The position of the label. If not defined, the label will default to the bottom of the image. Possible values are:
• t
• b
• w: The width of the image. If not defined, this will default to the natural width of the image.
• h: The height of the image. If not defined, this will default to the natural height of the image.
• constraint: Determines if the image should constrain the node size. This setting also ensures the image maintains its original aspect ratio, adjusting the width (w) accordingly to the height (h). If not defined, this will default to off Possible values are:
• on
• off

If you want to resize an image, but keep the same aspect ratio, set h, and set constraint: on to constrain the aspect ratio. E.g.

mermaid
flowchart TD
  %% My image with a constrained aspect ratio
  A@{ img: "https://mermaid.js.org/favicon.svg", label: "My example image label", pos: "t", h: 60, constraint: "on" }

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

mermaid-example
flowchart LR
    A-->B

An open link

mermaid-example
flowchart LR
    A --- B

Text on links

mermaid-example
flowchart LR
    A-- This is the text! ---B

or

mermaid-example
flowchart LR
    A---|This is the text|B

A link with arrow head and text

mermaid-example
flowchart LR
    A-->|text|B

or

mermaid-example
flowchart LR
    A-- text -->B

Dotted link

mermaid-example
flowchart LR
   A-.->B;

Dotted link with text

mermaid-example
flowchart LR
   A-. text .-> B

Thick link

mermaid-example
flowchart LR
   A ==> B

Thick link with text

mermaid-example
flowchart LR
   A == text ==> B

An invisible link

This can be a useful tool in some instances where you want to alter the default positioning of a node.

mermaid-example
flowchart LR
    A ~~~ B

Chaining of links

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

mermaid-example
flowchart LR
   A -- text --> B -- text2 --> C

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

mermaid-example
flowchart LR
   a --> b & c--> d

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

mermaid-example
flowchart TB
    A & B--> C & D

If you describe the same diagram using 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.

mermaid
flowchart TB
    A --> C
    A --> D
    B --> C
    B --> D

Attaching an ID to Edges

Mermaid now supports assigning IDs to edges, similar to how IDs and metadata can be attached to nodes. This feature lays the groundwork for more advanced styling, classes, and animation capabilities on edges.

Syntax:

To give an edge an ID, prepend the edge syntax with the ID followed by an @ character. For example:

mermaid
flowchart LR
  A e1@--> B

In this example, e1 is the ID of the edge connecting A to B. You can then use this ID in later definitions or style statements, just like with nodes.

Turning an Animation On

Once you have assigned an ID to an edge, you can turn on animations for that edge by defining the edge’s properties:

mermaid
flowchart LR
  A e1@==> B
  e1@{ animate: true }

This tells Mermaid that the edge e1 should be animated.

Selecting Type of Animation

In the initial version, two animation speeds are supported: fast and slow. Selecting a specific animation type is a shorthand for enabling animation and setting the animation speed in one go.

Examples:

mermaid
flowchart LR
  A e1@--> B
  e1@{ animation: fast }

This is equivalent to { animate: true, animation: fast }.

Using classDef Statements for Animations

You can also animate edges by assigning a class to them and then defining animation properties in a classDef statement. For example:

mermaid
flowchart LR
  A e1@--> B
  classDef animate stroke-dasharray: 9,5,stroke-dashoffset: 900,animation: dash 25s linear infinite;
  class e1 animate

In this snippet:

• e1@--> creates an edge with ID e1.
• classDef animate defines a class named animate with styling and animation properties.
• class e1 animate applies the animate class to the edge e1.

Note on Escaping Commas: When setting the stroke-dasharray property, remember to escape commas as \, since commas are used as delimiters in Mermaid’s style definitions.

New arrow types

There are new types of arrows supported:

• circle edge
• cross edge

Circle edge example

mermaid-example
flowchart LR
    A --o B

Cross edge example

mermaid-example
flowchart LR
    A --x B

Multi directional arrows

There is the possibility to use multidirectional arrows.

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

Minimum length of a link

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:

mermaid-example
flowchart 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:

mermaid-example
flowchart 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:

mermaid-example
flowchart LR
    id1["This is the (text) in the box"]

Entity codes to escape characters

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

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

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:

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

You can also set an explicit id for the subgraph.

mermaid-example
flowchart TB
    c1-->a2
    subgraph ide1 [one]
    a1-->a2
    end

flowcharts

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

mermaid-example
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

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.

mermaid-example
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

Limitation

If any of a subgraph's nodes are linked to the outside, subgraph direction will be ignored. Instead the subgraph will inherit the direction of the parent graph:

mermaid-example
flowchart LR
    subgraph subgraph1
        direction TB
        top1[top] --> bottom1[bottom]
    end
    subgraph subgraph2
        direction TB
        top2[top] --> bottom2[bottom]
    end
    %% ^ These subgraphs are identical, except for the links to them:

    %% Link *to* subgraph1: subgraph1 direction is maintained
    outside --> subgraph1
    %% Link *within* subgraph2:
    %% subgraph2 inherits the direction of the top-level graph (LR)
    outside ---> top2

Markdown Strings

The "Markdown Strings" feature enhances flowcharts and mind maps by offering a more versatile string type, which supports text formatting options such as bold and italics, and automatically wraps text within labels.

mermaid-example
---
config:
  flowchart:
    htmlLabels: false
---
flowchart LR
subgraph "One"
  a("`The **cat**
  in the hat`") -- "edge label" --> b{{"`The **dog** in the hog`"}}
end
subgraph "`**Two**`"
  c("`The **cat**
  in the hat`") -- "`Bold **edge label**`" --> d("The dog in the hog")
end

Formatting:

• For bold text, use double asterisks (**) before and after the text.
• For italics, use single asterisks (*) before and after the text.
• With traditional strings, you needed to add <br> tags for text to wrap in nodes. However, markdown strings automatically wrap text when it becomes too long and allows you to start a new line by simply using a newline character instead of a <br> tag.

This feature is applicable to node labels, edge labels, and subgraph labels.

The auto wrapping can be disabled by using

---
config:
  markdownAutoWrap: false
---
graph LR

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>
  window.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.

mermaid-example
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 C call callback() "Tooltip for a callback"
    click D href "https://www.github.com" "This is a tooltip for 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):

mermaid-example
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

Beginner's tip—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>
    window.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

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

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, 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;

It is also possible to add style to multiple links in a single statement, by separating link numbers with commas:

linkStyle 1,2,7 color:blue;

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, bumpX, bumpY, cardinal, catmullRom, linear, monotoneX, monotoneY, natural, step, stepAfter, and stepBefore.

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

Line styling can be achieved in two ways:

1. Change the curve style of all the lines
2. Change the curve style of a particular line

Diagram level curve style

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

---
config:
  flowchart:
    curve: stepBefore
---
graph LR

Edge level curve style using Edge IDs (v11.10.0+)

You can assign IDs to edges. After assigning an ID you can modify the line style by modifying the edge's curve property using the following syntax:

mermaid
flowchart LR
    A e1@==> B
    A e2@--> C
    e1@{ curve: linear }
    e2@{ curve: natural }

info
Any edge curve style modified at the edge level overrides the diagram level style.

info
If the same edge is modified multiple times the last modification will be rendered.

Styling a node

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

mermaid-example
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

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;

Also, it is possible to define style to multiple classes in one statement:

    classDef firstClassName,secondClassName font-size:12pt;

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:

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

This form can be used when declaring multiple links between nodes:

mermaid-example
flowchart LR
    A:::foo & B:::bar --> C:::foobar
    classDef foo stroke:#f00
    classDef bar stroke:#0f0
    classDef foobar stroke:#00f

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

mermaid-example
flowchart 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 accessed via the syntax fa:#icon class name#.

mermaid-example
flowchart 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?)

There are two ways to display these FontAwesome icons:

Register FontAwesome icon packs (v11.7.0+)

You can register your own FontAwesome icon pack following the "Registering icon packs" instructions.

Supported prefixes: fa, fab, fas, far, fal, fad.

note
Note that it will fall back to FontAwesome CSS if FontAwesome packs are not registered.

Register FontAwesome CSS

Mermaid supports Font Awesome if the CSS is included on the website. Mermaid does not have any restriction on the version of Font Awesome that can be used.

Please refer the Official Font Awesome Documentation on how to include it in your website.

Adding this snippet in the <head> would add support for Font Awesome v6.5.1

html
<link
  href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/6.5.1/css/all.min.css"
  rel="stylesheet"
/>

Custom icons

It is possible to use custom icons served from Font Awesome as long as the website imports the corresponding kit.

Note that this is currently a paid feature from Font Awesome.

For custom icons, you need to use the fak prefix.

Example

flowchart TD
    B[fa:fa-twitter] %% standard icon
    B-->E(fak:fa-custom-icon-name) %% custom icon

And trying to render it

mermaid-example
flowchart TD
    B["fa:fa-twitter for peace"]
    B-->C["fab:fa-truck-bold a custom icon"]

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 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.

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

Configuration

Renderer

The layout of the diagram is done with the renderer. The default renderer is dagre.

Starting with Mermaid version 9.4, you can use an alternate renderer named elk. The elk renderer is better for larger and/or more complex diagrams.

The _elk_ renderer is an experimental feature. You can change the renderer to elk by adding this directive:

config:
  flowchart:
    defaultRenderer: "elk"

note
Note that the site needs to use mermaid version 9.4+ for this to work and have this featured enabled in the lazy-loading configuration.

Width

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%
}

<!--- cspell:ignore lagom --->