1.3.0 • Public • Published

SVG Sequence Diagram

A tool for creating sequence diagrams from a Domain-Specific Language. Runs in nodejs and browsers.

See it in action in the online editor

The core rendering capability is also available as a library:

npm install --save svg-sequence-diagram
import { SequenceDiagram } from 'svg-sequence-diagram';

const myDiagram = new SequenceDiagram(`
title Foo
A -> B
B -> A


See here for full API documentation.

Or generate SVGs from the commandline:

npx svg-sequence-diagram < source.txt > diagram.svg


Simple Usage

Simple Usage preview

title Labyrinth

Bowie -> Goblin: You remind me of the babe
Goblin -> Bowie: What babe?
Bowie -> Goblin: The babe with the power
Goblin -> Bowie: What power?
note right of Bowie, Goblin: Most people get muddled here!
Bowie -> Goblin: "The power of voodoo"
Goblin -> Bowie: "Who-do?"
Bowie -> Goblin: You do!
Goblin -> Bowie: Do what?
Bowie -> Goblin: Remind me of the babe!

Bowie -> Audience: Sings

terminators box

Connection Types

Connection Types preview

title Connection Types

begin Foo, Bar, Baz

Foo -> Bar: Simple arrow
Bar --> Baz: Dashed arrow
Foo <- Bar: Reversed arrow
Bar <-- Baz: Reversed & dashed
Foo <-> Bar: Double arrow
Bar <--> Baz: Double dashed arrow

# An arrow with no label:
Foo -> Bar

Bar ->> Baz: Different arrow
Foo <<--> Bar: Mix of arrows

Bar -> Bar: Bar talks to itself

Foo -> +Bar: Foo asks Bar
-Bar --> Foo: and Bar replies

Bar -x Baz: Lost message

# Arrows leaving on the left and right of the diagram
[ -> Foo: From the left
[ <- Foo: To the left
Foo -> ]: To the right
Foo <- ]: From the right
[ ~> ]: Wavy left to right!
# (etc.)


Dividers preview

title Dividers

begin Foo, Bar, Baz

Foo -> +Bar


Bar -> +Baz

divider delay: This takes a while

-Baz --> Bar

divider tear with height 20: Lots of stuff happens

-Bar --> Foo

Notes & State

Notes and State preview

title Note Placements

begin Foo, Bar

note over Foo: Foo says something
note left of Foo: Stuff
note right of Bar: More stuff
note over Foo, Bar: "Foo and Bar
on multiple lines"
note between Foo, Bar: Link

# in long diagrams, we can add reminders of which agent is which:

text right: "Comments\nOver here!"

state over Foo: Foo is ponderous


Logic preview

title At the Bank

begin Person, ATM, Bank
Person -> ATM: Request money
ATM -> Bank: Check funds
if fraud detected
  Bank -> Police: "Get 'em!"
  Police -> Person: "You're nicked"
  end Police
else if sufficient funds
  ATM -> Bank: Withdraw funds
  repeat until "all requested money
                has been handed over"
    ATM -> Person: Dispense note
  ATM -> Person: Error

Label Templates

Label Templates preview

autolabel "[<inc>] <label>"

begin "Underpants\nGnomes" as A
A <- ]: Collect underpants
A <-> ]: ???
A <- ]: Profit!

Multiline Text

Multiline Text preview

title "My Multiline

begin Foo, Bar

note over Foo: "Also possible\nwith escapes"

Foo -> Bar: "Lines of text\non this arrow"

if "Even multiline\ninside conditions like this"
  Foo -> "Multiline\nagent"

state over Foo: "Newlines here,


Themes preview

theme sketch

title Mockup

A thing -> +Another thing: Something happens
-Another thing --> A thing: With some response
note right of Another thing: Find out what happens here
end Another thing

Short-Lived Agents

Short Lived Agents preview

title "Baz doesn't live long"

note over Foo, Bar: Using begin / end

begin Baz
Bar -> Baz
Baz -> Foo
end Baz

note over Foo, Bar: Using * / !

# * and ! cause agents to be
# created and destroyed inline
Bar -> *Baz: make Baz
Foo <- !Baz: end Baz

# Foo and Bar end with black bars
terminators bar
# (options are: box, bar, cross, fade, none)

Agent Aliases

Agent Aliases preview

define My complicated agent name as A
define "Another agent name,
and this one's multi-line!" as B

A -> B: this is much easier
A <- B: than writing the whole name


Markdown preview

define "Name with
**bold** and _italic_" as A
define "Also `code`
and ~strikeout~" as B

A -> B: "_**basic markdown
is supported!**_"

Alternative Agent Ordering

Alternative Agent Ordering preview

define Baz, Foo

Foo -> Bar
Bar -> Baz

Agent Types

Agent Types preview

begin User, Application, PostgreSQL

User -> +Application
Application -> +PostgreSQL
-PostgreSQL --> Application
-Application --> User

User is a person
PostgreSQL is a database

Asynchronous Communication

Asynchronous Communication preview

begin Initiator as I, Receiver as R

# the '' syntax allows connections
# to span multiple lines

I -> ...fin1
...fin1 -> R: FIN

# they can even inter-mix!
R -> ...ack1
R -> ...fin2
...ack1 -> I: ACK
...fin2 -> I: FIN

!I -> ...ack2
...ack2 -> !R: ACK

Simultaneous Actions (Beta!)

This is a work-in-progress feature. There are situations where this can lead to ugly / unreadable overlapping content.

Simultaneous Actions preview

begin A, B, C, D
A -> C

# Define a marker which can be returned to later

some primary process:
A -> B
B -> A
A -> B
B -> A

# Return to the defined marker
# (should be interpreted as no-higher-then the marker; may be
# pushed down to keep relative action ordering consistent)

simultaneously with some primary process:
C -> D
D -> C
end D
C -> A

# The marker name is optional; using "simultaneously:" with no
# marker will jump to the top of the entire sequence.

DSL Basics

Comments begin with a # and end at the next newline:

# This is a comment

Meta data can be provided with particular keywords:

title "My title here"

Quoting strings is usually optional, for example these are the same:

title "My title here"
title My title here
title "My title" here
title "My" "title" "here"

Each non-metadata line represents a step in the sequence, in order.

# Draw an arrow from agent "Foo Bar" to agent "Zig Zag" with a label:
# (implicitly creates the agents if they do not already exist)

Foo Bar -> Zig Zag: Do a thing

# With quotes, this is the same as:

"Foo Bar" -> "Zig Zag": "Do a thing"

Blocks surround steps, and can nest:

if something
  Foo -> Bar
else if something else
  Foo -> Baz
  if more stuff
    Baz -> Zig

(indentation is ignored)

Running a Server

If you want to run an online renderer (like, take a look at


Contributions are welcome!

If you find a bug or desire a new feature, feel free to report it in the GitHub issue tracker, or write the code yourself and make a pull request.

For more details on contributing, see the file.




npm i svg-sequence-diagram

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  • davidje13