Sequence Diagram syntax and features

Sequence diagram

Sequence diagrams in PlantUML are defined entirely in text. You write the participants and the messages they exchange; the layout, spacing, and arrows are handled for you.

Text in, diagram out. The source is the single point of truth, what you read is what gets rendered.
Easy to edit. Adjust a line of text instead of dragging boxes around.
Quick to iterate. Live preview tools render as you type, so you catch mistakes early.

See common commands for features available across all diagram types.

Basic Examples

In PlantUML sequence diagrams, the -> sequence denotes a message sent between two participants, which are automatically recognized and do not need to be declared beforehand.

Utilize dotted arrows by employing the --> sequence, offering a distinct visualization in your diagrams.

To improve readability without affecting the visual representation, use reverse arrows like <- or <--. However, be aware that this is specifically for sequence diagrams and the rules differ for other diagram types.

@startuml
Alice -> Bob: Authentication Request
Bob --> Alice: Authentication Response

Alice -> Bob: Another authentication Request
Alice <-- Bob: Another authentication Response
@enduml

Declaring participant

If the keyword participant is used to declare a participant, more control on that participant is possible.

The order of declaration will be the (default) order of display.

Using these other keywords to declare participants will change the shape of the participant representation:

actor
boundary
control
entity
database
collections
queue

Syntax:

<participant_type> <label> as <alias>

@startuml
participant Participant as Foo
actor       Actor       as Foo1
boundary    Boundary    as Foo2
control     Control     as Foo3
entity      Entity      as Foo4
database    Database    as Foo5
collections Collections as Foo6
queue       Queue       as Foo7
Foo -> Foo1 : To actor 
Foo -> Foo2 : To boundary
Foo -> Foo3 : To control
Foo -> Foo4 : To entity
Foo -> Foo5 : To database
Foo -> Foo6 : To collections
Foo -> Foo7: To queue
@enduml

Rename a participant using the as keyword.

You can also change the background color of actor or participant.

@startuml
actor Bob #red
' The only difference between actor
'and participant is the drawing
participant Alice
participant "I have a really\nlong name" as L #99FF99
/' You can also declare:
   participant L as "I have a really\nlong name"  #99FF99
  '/

Alice->Bob: Authentication Request
Bob->Alice: Authentication Response
Bob->L: Log transaction
@enduml

You can use the order keyword to customize the display order of participants.

@startuml
participant Last order 30
participant Middle order 20
participant First order 10
@enduml

Declaring participant on multiline

You can declare participant on multi-line.

@startuml
participant Participant [
    =Title
    ----
    ""SubTitle""
]

participant Bob

Participant -> Bob
@enduml

[Ref. QA-15232]

Use non-letters in participants

You can use quotes to define participants. And you can use the as keyword to give an alias to those participants.

@startuml
Alice -> "Bob()" : Hello
"Bob()" -> "This is very\nlong" as Long
' You can also declare:
' "Bob()" -> Long as "This is very\nlong"
Long --> "Bob()" : ok
@enduml

Message to Self

A participant can send a message to itself.

It is also possible to have multi-line using \n.

@startuml
Alice -> Alice: This is a signal to self.\nIt also demonstrates\nmultiline \ntext
@enduml

@startuml
Alice <- Alice: This is a signal to self.\nIt also demonstrates\nmultiline \ntext
@enduml

[Ref. QA-1361]

Text alignment

Text alignment on arrows can be set to left, right or center using skinparam sequenceMessageAlign.

You can also use direction or reverseDirection to align text depending on arrow direction. Further details and examples of this are available on the skinparam page.

@startuml
skinparam sequenceMessageAlign right
Bob -> Alice : Request
Alice -> Bob : Response
@enduml

Text of response message below the arrow

You can put the text of the response message below the arrow, with the skinparam responseMessageBelowArrow true command.

@startuml
skinparam responseMessageBelowArrow true
Bob -> Alice : hello
Bob <- Alice : ok
@enduml

Change Actor style

You can change the actor style from stick man (by default) to:

an awesome man with the skinparam actorStyle awesome command;
a hollow man with the skinparam actorStyle hollow command.

Stick man (by default)

@startuml
actor Alice
actor Bob
Alice -> Bob : hello
hide footbox
@enduml

Awesome man

@startuml
skinparam actorStyle awesome
actor Alice
actor Bob
Alice -> Bob : hello
hide footbox
@enduml

[Ref. QA-10493]

Hollow man

@startuml
skinparam actorStyle Hollow
actor Alice
actor Bob
Alice -> Bob : hello
hide footbox
@enduml

[Ref. PR#396]

Change arrow style

You can change arrow style by several ways:

add a final x to denote a lost message
use \ or / instead of < or > to have only the bottom or top part of the arrow
repeat the arrow head (for example, >> or //) head to have a thin drawing
use -- instead of - to have a dotted arrow
add a final "o" at arrow head
use bidirectional arrow <->

@startuml
Bob ->x Alice
Bob -> Alice
Bob ->> Alice
Bob -\ Alice
Bob \\- Alice
Bob //-- Alice

Bob ->o Alice
Bob o\\-- Alice

Bob <-> Alice
Bob <->o Alice
@enduml

Change arrow color

You can change the color of individual arrows using the following notation:

@startuml
Bob -[#red]> Alice : hello
Alice -[#0000FF]->Bob : ok
@enduml

Message sequence numbering

The keyword autonumber is used to automatically add an incrementing number to messages.

@startuml
autonumber
Bob -> Alice : Authentication Request
Bob <- Alice : Authentication Response
@enduml

You can specify a startnumber with autonumber <start> , and also an increment with autonumber <start> <increment>.

@startuml
autonumber
Bob -> Alice : Authentication Request
Bob <- Alice : Authentication Response

autonumber 15
Bob -> Alice : Another authentication Request
Bob <- Alice : Another authentication Response

autonumber 40 10
Bob -> Alice : Yet another authentication Request
Bob <- Alice : Yet another authentication Response

@enduml

You can specify a format for your number by using between double-quote.

The formatting is done with the Java class DecimalFormat (0 means digit, # means digit and zero if absent).

You can use some html tag in the format.

@startuml
autonumber "<b>[000]"
Bob -> Alice : Authentication Request
Bob <- Alice : Authentication Response

autonumber 15 "<b>(<u>##</u>)"
Bob -> Alice : Another authentication Request
Bob <- Alice : Another authentication Response

autonumber 40 10 "<font color=red><b>Message 0  "
Bob -> Alice : Yet another authentication Request
Bob <- Alice : Yet another authentication Response

@enduml

You can also use autonumber stop and autonumber resume <increment> <format> to respectively pause and resume automatic numbering.

@startuml
autonumber 10 10 "<b>[000]"
Bob -> Alice : Authentication Request
Bob <- Alice : Authentication Response

autonumber stop
Bob -> Alice : dummy

autonumber resume "<font color=red><b>Message 0  "
Bob -> Alice : Yet another authentication Request
Bob <- Alice : Yet another authentication Response

autonumber stop
Bob -> Alice : dummy

autonumber resume 1 "<font color=blue><b>Message 0  "
Bob -> Alice : Yet another authentication Request
Bob <- Alice : Yet another authentication Response
@enduml

Your startnumber can also be a 2 or 3 digit sequence using a field delimiter such as ., ;, ,, : or a mix of these. For example: 1.1.1 or 1.1:1.

Automatically the last digit will increment.

To increment the first digit, use: autonumber inc A. To increment the second digit, use: autonumber inc B.

@startuml
autonumber 1.1.1
Alice -> Bob: Authentication request
Bob --> Alice: Response

autonumber inc A
'Now we have 2.1.1
Alice -> Bob: Another authentication request
Bob --> Alice: Response

autonumber inc B
'Now we have 2.2.1
Alice -> Bob: Another authentication request
Bob --> Alice: Response

autonumber inc A
'Now we have 3.1.1
Alice -> Bob: Another authentication request
autonumber inc B
'Now we have 3.2.1
Bob --> Alice: Response
@enduml

You can also use the value of autonumber with the %autonumber% variable:

@startuml
autonumber 10
Alice -> Bob
note right
  the <U+0025>autonumber<U+0025> works everywhere.
  Here, its value is ** %autonumber% **
end note
Bob --> Alice: //This is the response %autonumber%//
@enduml

[Ref. QA-7119]

Page Title, Header and Footer

The title keyword is used to add a title to the page.

Pages can display headers and footers using header and footer.

@startuml

header Page Header
footer Page %page% of %lastpage%

title Example Title

Alice -> Bob : message 1
Alice -> Bob : message 2

@enduml

Splitting diagrams

With `newpage`

The newpage keyword is used to split a diagram into several images.

You can put a title for the new page just after the newpage keyword. This title overrides the previously specified title if any.

This is very handy with Word to print long diagram on several pages.

(Note: this really does work. Only the first page is shown below, but it is a display artifact.)

@startuml

Alice -> Bob : message 1
Alice -> Bob : message 2

newpage

Alice -> Bob : message 3
Alice -> Bob : message 4

newpage A title for the\nlast page

Alice -> Bob : message 5
Alice -> Bob : message 6
@enduml

`%page%` and `%lastpage%` variables

@startuml
footer This is %page% of %lastpage%
Alice --> Bob : A1
newpage
Alice --> Bob : A2
newpage
Alice --> Bob : A3
newpage
Alice --> Bob : A4
@enduml

[Ref. QA-6699]

Ignore newpage

You can use the ignore newpage command to show all the pages, as if there was no newpage.

@startuml

ignore newpage

Alice -> Bob : message 1
Alice -> Bob : message 2

newpage

Alice -> Bob : message 3
Alice -> Bob : message 4

newpage A title for the\nlast page

Alice -> Bob : message 5
Alice -> Bob : message 6
@enduml

Grouping message

It is possible to group messages together using the following keywords:

alt/else
opt
loop
par
break
critical
group, followed by a text to be displayed

It is possible to add a text that will be displayed into the header (for group, see next paragraph 'Secondary group label').

The end keyword is used to close the group.

Note that it is possible to nest groups.

@startuml
Alice -> Bob: Authentication Request

alt successful case

    Bob -> Alice: Authentication Accepted

else some kind of failure

    Bob -> Alice: Authentication Failure
    group My own label
    Alice -> Log : Log attack start
        loop 1000 times
            Alice -> Bob: DNS Attack
        end
    Alice -> Log : Log attack end
    end

else Another type of failure

   Bob -> Alice: Please repeat

end
@enduml

Secondary group label

For group, it is possible to add, between[ and ], a secondary text or label that will be displayed into the header.

@startuml
Alice -> Bob: Authentication Request
Bob -> Alice: Authentication Failure
group My own label [My own label 2]
    Alice -> Log : Log attack start
    loop 1000 times
        Alice -> Bob: DNS Attack
    end
    Alice -> Log : Log attack end
end
@enduml

[Ref. QA-2503]

Partition across the entire width

You can use partition command to group messages horizontally across the entire width (full-width).

Messages are not grouped horizontally across the entire width (by default)

@startuml
participant a

partition p1
b -> c: msg
c --> b: OK
note right: Some right note
end

partition p2
a -> b: msg
note left: Some left note
end
@enduml

Grouping messages horizontally across the entire width (with `teoz` mode)

@startuml
!pragma teoz true
participant a

partition p1
b -> c: msg
c --> b: OK
note right: Some right note
end

partition p2
a -> b: msg
note left: Some left note
end
@enduml

[Ref. GH-589]

Notes on messages

It is possible to put notes on message using the note left or note right keywords just after the message.

You can have a multi-line note using the end note keywords.

@startuml
Alice->Bob : hello
note left: this is a first note

Bob->Alice : ok
note right: this is another note

Bob->Bob : I am thinking
note left
a note
can also be defined
on several lines
end note
@enduml

Some other notes

It is also possible to place notes relative to participant with note left of , note right of or note over keywords.

It is possible to highlight a note by changing its background color.

You can also have a multi-line note using the end note keywords.

@startuml
participant Alice
participant Bob
note left of Alice #aqua
This is displayed
left of Alice.
end note

note right of Alice: This is displayed right of Alice.

note over Alice: This is displayed over Alice.

note over Alice, Bob #FFAAAA: This is displayed\n over Bob and Alice.

note over Bob, Alice
This is yet another
example of
a long note.
end note
@enduml

Changing notes shape [hnote, rnote]

You can use hnote and rnote keywords to change note shapes :

hnote for hexagonal note;
rnote for rectangle note.

@startuml
caller -> server : conReq
hnote over caller : idle
caller <- server : conConf
rnote over server
 "r" as rectangle
 "h" as hexagon
endrnote
rnote over server
 this is
 on several
 lines
endrnote
hnote over caller
 this is
 on several
 lines
endhnote
@enduml

[Ref. QA-1765]

Note over all participants [across]

You can directly make a note over all participants, with the syntax:

note across: note_description

@startuml
Alice->Bob:m1
Bob->Charlie:m2
note over Alice, Charlie: Old method for note over all part. with:\n ""note over //FirstPart, LastPart//"".
note across: New method with:\n""note across""
Bob->Alice
hnote across:Note across all part.
@enduml

[Ref. QA-9738]

Several notes aligned at the same level [/]

You can make several notes aligned at the same level, with the syntax /:

without / (by default, the notes are not aligned)

@startuml
note over Alice : initial state of Alice
note over Bob : initial state of Bob
Bob -> Alice : hello
@enduml

with / (the notes are aligned)

@startuml
note over Alice : initial state of Alice
/ note over Bob : initial state of Bob
Bob -> Alice : hello
@enduml

[Ref. QA-354]

Creole and HTML

It is also possible to use creole formatting:

@startuml
participant Alice
participant "The **Famous** Bob" as Bob

Alice -> Bob : hello --there--
... Some ~~long delay~~ ...
Bob -> Alice : ok
note left
  This is **bold**
  This is //italics//
  This is ""monospaced""
  This is --stroked--
  This is __underlined__
  This is ~~waved~~
end note

Alice -> Bob : A //well formatted// message
note right of Alice
 This is <back:cadetblue><size:18>displayed</size></back>
 __left of__ Alice.
end note
note left of Bob
 <u:red>This</u> is <color #118888>displayed</color>
 **<color purple>left of</color> <s:red>Alice</strike> Bob**.
end note
note over Alice, Bob
 <w:#FF33FF>This is hosted</w> by <img:https://plantuml.com/sourceforge.jpg>
end note
@enduml

Divider or separator

If you want, you can split a diagram using == separator to divide your diagram into logical steps.

@startuml

== Initialization ==

Alice -> Bob: Authentication Request
Bob --> Alice: Authentication Response

== Repetition ==

Alice -> Bob: Another authentication Request
Alice <-- Bob: another authentication Response

@enduml

Reference

You can use reference in a diagram, using the keyword ref over.

@startuml
participant Alice
actor Bob

ref over Alice, Bob : init

Alice -> Bob : hello

ref over Bob
  This can be on
  several lines
end ref
@enduml

Delay

You can use ... to indicate a delay in the diagram. And it is also possible to put a message with this delay.

@startuml

Alice -> Bob: Authentication Request
...
Bob --> Alice: Authentication Response
...5 minutes later...
Bob --> Alice: Good Bye !

@enduml

Text wrapping

To break long messages, you can manually add \n in your text.

Another option is to use maxMessageSize setting:

@startuml
skinparam maxMessageSize 50
participant a
participant b
a -> b :this\nis\nmanually\ndone
a -> b :this is a very long message on several words
@enduml

Message text spans beyond the involved participants

You can use sequenceMessageSpan command to allow message text to span beyond the involved participants.

Without `sequenceMessageSpan` (by default)

@startuml
ParticipantNumber1 -> ParticipantNumber2 : this is a very long message that is very long
ParticipantNumber1 -> ParticipantNumber1 : this is a very long message that is very long 
ParticipantNumber2 -> ParticipantNumber3 : foo2
@enduml

With `sequenceMessageSpan` (on `teoz` mode)

@startuml
!pragma teoz true
!pragma sequenceMessageSpan true

ParticipantNumber1 -> ParticipantNumber2 : this is a very long message that is very long
ParticipantNumber1 -> ParticipantNumber1 : this is a very long message that is very long 
ParticipantNumber2 -> ParticipantNumber3 : foo2
@enduml

[Ref. GH-2386]

Space

You can use ||| to indicate some spacing in the diagram.

It is also possible to specify a number of pixel to be used.

@startuml

Alice -> Bob: message 1
Bob --> Alice: ok
|||
Alice -> Bob: message 2
Bob --> Alice: ok
||45||
Alice -> Bob: message 3
Bob --> Alice: ok

@enduml

Lifeline Activation and Destruction

The activate and deactivate are used to denote participant activation.

Once a participant is activated, its lifeline appears.

The activate and deactivate apply on the previous message.

The destroy denote the end of the lifeline of a participant.

@startuml
participant User

User -> A: DoWork
activate A

A -> B: << createRequest >>
activate B

B -> C: DoWork
activate C
C --> B: WorkDone
destroy C

B --> A: RequestCreated
deactivate B

A -> User: Done
deactivate A

@enduml

Nested lifeline can be used, and it is possible to add a color on the lifeline.

@startuml
participant User

User -> A: DoWork
activate A #FFBBBB

A -> A: Internal call
activate A #DarkSalmon

A -> B: << createRequest >>
activate B

B --> A: RequestCreated
deactivate B
deactivate A
A -> User: Done
deactivate A

@enduml

Autoactivation is possible and works with the return keywords:

@startuml
autoactivate on
alice -> bob : hello
bob -> bob : self call
bill -> bob #005500 : hello from thread 2
bob -> george ** : create
return done in thread 2
return rc
bob -> george !! : delete
return success

@enduml

Return

Command return generates a return message with optional text label.

The return point is that which caused the most recent life-line activation.

The syntax is return label where label if provided is any string acceptable for conventional messages.

@startuml
Bob -> Alice : hello
activate Alice
Alice -> Alice : some action
return bye
@enduml

Participant creation

You can use the create keyword just before the first reception of a message to emphasize the fact that this message is actually creating this new object.

@startuml
Bob -> Alice : hello

create Other
Alice -> Other : new

create control String
Alice -> String
note right : You can also put notes!

Alice --> Bob : ok

@enduml

Shortcut syntax for activation, deactivation, creation

Immediately after specifying the target participant, the following syntax can be used:

++ Activate the target (optionally a color may follow this)
-- Deactivate the source
** Create an instance of the target
!! Destroy an instance of the target

@startuml
alice -> bob ++ : hello
bob -> bob ++ : self call
bob -> bib ++  #005500 : hello
bob -> george ** : create
return done
return rc
bob -> george !! : delete
return success
@enduml

Then you can mix activation and deactivation, on same line:

@startuml
alice   ->  bob     ++   : hello1
bob     ->  charlie --++ : hello2
charlie --> alice   --   : ok
@enduml

@startuml
alice -> bob   --++ #gold: hello
bob   -> alice --++ #gold: you too
alice -> bob   --: step1
alice -> bob   : step2
@enduml

[Ref. QA-4834, QA-9573 and QA-13234]

Incoming and outgoing messages

You can use incoming or outgoing arrows if you want to focus on a part of the diagram.

Use square brackets to denote the left "[" or the right "]" side of the diagram.

@startuml
[-> A: DoWork

activate A

A -> A: Internal call
activate A

A ->] : << createRequest >>

A<--] : RequestCreated
deactivate A
[<- A: Done
deactivate A
@enduml

You can also have the following syntax:

@startuml
participant Alice
participant Bob #lightblue
Alice -> Bob
Bob -> Carol
...
[-> Bob
[o-> Bob
[o->o Bob
[x-> Bob
...
[<- Bob
[x<- Bob
...
Bob ->]
Bob ->o]
Bob o->o]
Bob ->x]
...
Bob <-]
Bob x<-]

@enduml

Short arrows for incoming and outgoing messages

You can have short arrows with using ?.

@startuml
?-> Alice    : ""?->""\n**short** to actor1
[-> Alice    : ""[->""\n**from start** to actor1
[-> Bob      : ""[->""\n**from start** to actor2
?-> Bob      : ""?->""\n**short** to actor2
Alice ->]    : ""->]""\nfrom actor1 **to end**
Alice ->?    : ""->?""\n**short** from actor1
Alice -> Bob : ""->"" \nfrom actor1 to actor2
@enduml

[Ref. QA-310]

Anchors and Duration

With teoz it is possible to add anchors to the diagram and use the anchors to specify duration time.

@startuml
!pragma teoz true

{start} Alice -> Bob : start doing things during duration
Bob -> Max : something
Max -> Bob : something else
{end} Bob -> Alice : finish

{start} <-> {end} : some time

@enduml

You can use the -P command-line option to specify the pragma:

java -jar plantuml.jar -Pteoz=true

[Ref. issue-582]

Stereotypes and Spots

It is possible to add stereotypes to participants using << and >>.

In the stereotype, you can add a spotted character in a colored circle using the syntax (X,color).

@startuml

participant "Famous Bob" as Bob << Generated >>
participant Alice << (C,#ADD1B2) Testable >>

Bob->Alice: First message

@enduml

By default, the guillemet character is used to display the stereotype. You can change this behavious using the skinparam guillemet:

@startuml

skinparam guillemet false
participant "Famous Bob" as Bob << Generated >>
participant Alice << (C,#ADD1B2) Testable >>

Bob->Alice: First message

@enduml

@startuml

participant Bob << (C,#ADD1B2) >>
participant Alice << (C,#ADD1B2) >>

Bob->Alice: First message

@enduml

Position of the stereotypes

It is possible to define stereotypes position (top or bottom) with the command skinparam stereotypePosition.

Bottom postion

@startuml
skinparam stereotypePosition bottom

participant A<<st1>>
participant B<<st2>>
A --> B : stereo test
@enduml

[Ref. QA-18650]

More information on titles

You can use creole formatting in the title.

@startuml

title __Simple__ **communication** example

Alice -> Bob: Authentication Request
Bob -> Alice: Authentication Response

@enduml

You can add newline using \n in the title description.

@startuml

title __Simple__ communication example\non several lines

Alice -> Bob: Authentication Request
Bob -> Alice: Authentication Response

@enduml

You can also define title on several lines using title and end title keywords.

@startuml

title
 <u>Simple</u> communication example
 on <i>several</i> lines and using <font color=red>html</font>
 This is hosted by <img:sourceforge.jpg>
end title

Alice -> Bob: Authentication Request
Bob -> Alice: Authentication Response

@enduml

Participants encompass

It is possible to draw a box around some participants, using box and end box commands.

You can add an optional title or a optional background color, after the box keyword.

@startuml

box "Internal Service" #LightBlue
participant Bob
participant Alice
end box
participant Other

Bob -> Alice : hello
Alice -> Other : hello

@enduml

It is also possible to nest boxes - to draw a box within a box - when using the teoz rendering engine, for example:

@startuml

!pragma teoz true
box "Internal Service" #LightBlue
participant Bob
box "Subteam"
participant Alice
participant John
end box

end box
participant Other

Bob -> Alice : hello
Alice -> John : hello
John -> Other: Hello

@enduml

Removing Foot Boxes

You can use the hide footbox keywords to remove the foot boxes of the diagram.

@startuml

hide footbox
title Foot Box removed

Alice -> Bob: Authentication Request
Bob --> Alice: Authentication Response

@enduml

Skinparam

You can use the skinparam command to change colors and fonts for the drawing.

You can use this command:

In the diagram definition, like any other commands,
In an included file,
In a configuration file, provided in the command line or the ANT task.

You can also change other rendering parameter, as seen in the following examples:

@startuml
skinparam sequenceArrowThickness 2
skinparam roundcorner 20
skinparam maxmessagesize 60
skinparam sequenceParticipant underline

actor User
participant "First Class" as A
participant "Second Class" as B
participant "Last Class" as C

User -> A: DoWork
activate A

A -> B: Create Request
activate B

B -> C: DoWork
activate C
C --> B: WorkDone
destroy C

B --> A: Request Created
deactivate B

A --> User: Done
deactivate A

@enduml

@startuml
skinparam backgroundColor #EEEBDC
!option handwritten true

skinparam sequence {
ArrowColor DeepSkyBlue
ActorBorderColor DeepSkyBlue
LifeLineBorderColor blue
LifeLineBackgroundColor #A9DCDF

ParticipantBorderColor DeepSkyBlue
ParticipantBackgroundColor DodgerBlue
ParticipantFontName Impact
ParticipantFontSize 17
ParticipantFontColor #A9DCDF

ActorBackgroundColor aqua
ActorFontColor DeepSkyBlue
ActorFontSize 17
ActorFontName Aapex
}

actor User
participant "First Class" as A
participant "Second Class" as B
participant "Last Class" as C

User -> A: DoWork
activate A

A -> B: Create Request
activate B

B -> C: DoWork
activate C
C --> B: WorkDone
destroy C

B --> A: Request Created
deactivate B

A --> User: Done
deactivate A

@enduml

Changing padding

It is possible to tune some padding settings.

@startuml
skinparam ParticipantPadding 20
skinparam BoxPadding 10

box "Foo1"
participant Alice1
participant Alice2
end box
box "Foo2"
participant Bob1
participant Bob2
end box
Alice1 -> Bob1 : hello
Alice1 -> Out : out
@enduml

[Ref. QA-5493]

Appendix: Examples of all arrow type

Normal arrow

@startuml
participant Alice as a
participant Bob   as b
a ->     b : ""->   ""
a ->>    b : ""->>  ""
a -\     b : ""-\   ""
a -\\    b : ""-\\\\""
a -/     b : ""-/   ""
a -//    b : ""-//  ""
a ->x    b : ""->x  ""
a x->    b : ""x->  ""
a o->    b : ""o->  ""
a ->o    b : ""->o  ""
a o->o   b : ""o->o ""
a <->    b : ""<->  ""
a o<->o  b : ""o<->o""
a x<->x  b : ""x<->x""
a ->>o   b : ""->>o ""
a -\o    b : ""-\o  ""
a -\\o   b : ""-\\\\o""
a -/o    b : ""-/o  ""
a -//o   b : ""-//o ""
a x->o   b : ""x->o ""
@enduml

Itself arrow

@startuml
participant Alice as a
participant Bob   as b
a ->     a : ""->   ""
a ->>    a : ""->>  ""
a -\     a : ""-\   ""
a -\\    a : ""-\\\\""
a -/     a : ""-/   ""
a -//    a : ""-//  ""
a ->x    a : ""->x  ""
a x->    a : ""x->  ""
a o->    a : ""o->  ""
a ->o    a : ""->o  ""
a o->o   a : ""o->o ""
a <->    a : ""<->  ""
a o<->o  a : ""o<->o""
a x<->x  a : ""x<->x""
a ->>o   a : ""->>o ""
a -\o    a : ""-\o  ""
a -\\o   a : ""-\\\\o""
a -/o    a : ""-/o  ""
a -//o   a : ""-//o ""
a x->o   a : ""x->o ""
@enduml

Incoming and outgoing messages (with '[', ']')

Incoming messages (with '[')

@startuml
participant Alice as a
participant Bob   as b
[->      b : ""[->   ""
[->>     b : ""[->>  ""
[-\      b : ""[-\   ""
[-\\     b : ""[-\\\\""
[-/      b : ""[-/   ""
[-//     b : ""[-//  ""
[->x     b : ""[->x  ""
[x->     b : ""[x->  ""
[o->     b : ""[o->  ""
[->o     b : ""[->o  ""
[o->o    b : ""[o->o ""
[<->     b : ""[<->  ""
[o<->o   b : ""[o<->o""
[x<->x   b : ""[x<->x""
[->>o    b : ""[->>o ""
[-\o     b : ""[-\o  ""
[-\\o    b : ""[-\\\\o""
[-/o     b : ""[-/o  ""
[-//o    b : ""[-//o ""
[x->o    b : ""[x->o ""
@enduml

Outgoing messages (with ']')

@startuml
participant Alice as a
participant Bob   as b
a ->]      : ""->]   ""
a ->>]     : ""->>]  ""
a -\]      : ""-\]   ""
a -\\]     : ""-\\\\]""
a -/]      : ""-/]   ""
a -//]     : ""-//]  ""
a ->x]     : ""->x]  ""
a x->]     : ""x->]  ""
a o->]     : ""o->]  ""
a ->o]     : ""->o]  ""
a o->o]    : ""o->o] ""
a <->]     : ""<->]  ""
a o<->o]   : ""o<->o]""
a x<->x]   : ""x<->x]""
a ->>o]    : ""->>o] ""
a -\o]     : ""-\o]  ""
a -\\o]    : ""-\\\\o]""
a -/o]     : ""-/o]  ""
a -//o]    : ""-//o] ""
a x->o]    : ""x->o] ""
@enduml

Short incoming and outgoing messages (with '?')

Short incoming (with '?')

@startuml
participant Alice as a
participant Bob   as b
a ->     b : //Long long label//
?->      b : ""?->   ""
?->>     b : ""?->>  ""
?-\      b : ""?-\   ""
?-\\     b : ""?-\\\\""
?-/      b : ""?-/   ""
?-//     b : ""?-//  ""
?->x     b : ""?->x  ""
?x->     b : ""?x->  ""
?o->     b : ""?o->  ""
?->o     b : ""?->o  ""
?o->o    b : ""?o->o ""
?<->     b : ""?<->  ""
?o<->o   b : ""?o<->o""
?x<->x   b : ""?x<->x""
?->>o    b : ""?->>o ""
?-\o     b : ""?-\o  ""
?-\\o    b : ""?-\\\\o ""
?-/o     b : ""?-/o  ""
?-//o    b : ""?-//o ""
?x->o    b : ""?x->o ""
@enduml

Short outgoing (with '?')

@startuml
participant Alice as a
participant Bob   as b
a ->     b : //Long long label//
a ->?      : ""->?   ""
a ->>?     : ""->>?  ""
a -\?      : ""-\?   ""
a -\\?     : ""-\\\\?""
a -/?      : ""-/?   ""
a -//?     : ""-//?  ""
a ->x?     : ""->x?  ""
a x->?     : ""x->?  ""
a o->?     : ""o->?  ""
a ->o?     : ""->o?  ""
a o->o?    : ""o->o? ""
a <->?     : ""<->?  ""
a o<->o?   : ""o<->o?""
a x<->x?   : ""x<->x?""
a ->>o?    : ""->>o? ""
a -\o?     : ""-\o?  ""
a -\\o?    : ""-\\\\o?""
a -/o?     : ""-/o?  ""
a -//o?    : ""-//o? ""
a x->o?    : ""x->o? ""
@enduml

Specific SkinParameter

By default

@startuml
Bob -> Alice : hello
...
Alice -> Bob : ok
@enduml

Style strictuml

To be conform to strict UML (for arrow style: emits triangle rather than sharp arrowheads), you can use:

skinparam style strictuml

@startuml
skinparam style strictuml
Bob -> Alice : hello
...
Alice -> Bob : ok
@enduml

[Ref. QA-1047]

LifelineStrategy

nosolid/solid

Since v1.2025.5, old skinparam lifelineStrategy solid no longer works. [Ref. QA-9016, QA-2794]

In order to have solid life line in sequence diagrams, you must now use style:

@startuml
<style>
lifeLine {
  LineStyle 0
}
delay {
  LineStyle 1-4
}
</style>
Bob -> Alice : hello
...
Alice -> Bob : ok
@enduml

[Ref. GH-2266 and GH-2662]

Hide unlinked participant

By default, all participants are displayed.

@startuml
participant Alice
participant Bob
participant Carol

Alice -> Bob : hello
@enduml

But you can hide unlinked participant.

@startuml
hide unlinked
participant Alice
participant Bob
participant Carol

Alice -> Bob : hello
@enduml

[Ref. QA-4247]

Color a group message

It is possible to color a group messages:

@startuml
Alice -> Bob: Authentication Request
alt#Gold #LightBlue Successful case
    Bob -> Alice: Authentication Accepted
else #Pink Failure
    Bob -> Alice: Authentication Rejected
end
@enduml

[Ref. QA-4750 and QA-6410]

Mainframe

@startuml
mainframe This is a **mainframe**
Alice->Bob : Hello
@enduml

[Ref. QA-4019 and Issue#148]

Slanted or odd arrows

You can use the (nn) option (before or after arrow) to make the arrows slanted, where nn is the number of shift pixels.

[Available only after v1.2022.6beta+]

@startuml
A ->(10) B: text 10
B ->(10) A: text 10

A ->(10) B: text 10
A (10)<- B: text 10
@enduml

@startuml
A ->(40) B++: Rq
B -->(20) A--: Rs
@enduml

[Ref. QA-14145]

@startuml
!pragma teoz true
A ->(50) C: Starts\nwhen 'B' sends
& B ->(25) C: \nBut B's message\n arrives before A's
@enduml

[Ref. QA-6684]

@startuml
!pragma teoz true

S1 ->(30) S2: msg 1\n
& S2 ->(30) S1: msg 2

note left S1: msg\nS2 to S1
& note right S2: msg\nS1 to S2
@enduml

[Ref. QA-1072]

Parallel messages (with teoz)

You can use the & teoz command to display parallel messages:

@startuml
!pragma teoz true
Alice -> Bob : hello
& Bob -> Charlie : hi
@enduml

(See also Teoz architecture)

Style for Solid Lifeline

By default

@startuml
Alice -> Bob : hello
...
Alice <- Bob : hello
@enduml

Solid Lifeline using style

@startuml
<style>
lifeLine {
  LineStyle 0
}
delay {
  LineStyle 1-4
}
</style>
Alice -> Bob : hello
...
Alice <- Bob : hello
@enduml

[Ref. GH-2266 and GH-2662]

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