Markdown ZenUML sequence maker

Draw a sequence diagram by writing it as code: name your participants, then write each call and return, and ZenUML lays out the lifelines, arrows and activation bars. Free in your browser, no sign-up.

ZenUML sequence syntax

A ZenUML block starts with the word zenuml. You list your participants, then write the story as calls between them. A call reads like code: one object calls a method on another, and the body of that call goes in braces. Here is each piece you can write.

Participants and messages

Declare a participant with a stereotype like @Actor or @Database, then send a plain message with A->B: text.

You write

zenuml
  @Actor Customer
  @Boundary Web
  Customer->Web: open page
  Web->Customer: show form

You get

Synchronous calls and returns

Write a method call as A->B.method(). Put the work it triggers in braces, and end with return value to send a result back.

You write

zenuml
  @Actor Customer
  @Boundary Web
  @Control OrderService
  Customer->Web.checkout() {
    Web->OrderService.create() {
      return orderId
    }
    return page
  }

You get

Creating an object

Write new B to create an object, or x = new B() to name the thing you made.

You write

zenuml
  @Control OrderService
  OrderService->OrderService.build() {
    order = new Order()
    return order
  }

You get

Cheat sheet

Write this	You get
`zenuml`	Start a ZenUML sequence
`title Text`	Title the diagram
`@Actor Name`	A participant drawn as an actor
`@Boundary Name`	A boundary (edge of the system)
`@Control Name`	A control (coordinating logic)
`@Entity Name`	An entity (a thing being worked on)
`@Database Name`	A database
`@Queue Name`	A message queue
`A->B: text`	A plain message from A to B
`A->B.method()`	A synchronous call to B.method()
`A->B.method() { … }`	A call whose body is the nested messages
`return value`	Return a result from the current call
`A->A: text`	A self message
`new B`	Create an object of B
`x = new B()`	Create B and name it x

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