PlantUML Syntax Reference

Overview

PlantUML is a Java-based tool that creates diagrams from text descriptions. It supports comprehensive UML diagrams and many non-UML diagram types.

Key advantages:

• Most comprehensive diagram support (15+ types)
• Mature C4 model integration with icons/sprites
• Extensive customization options
• Battle-tested (since 2009)

Requirements:

• Java Runtime Environment (JRE)
• GraphViz (for some diagram types)
• Or use Docker: docker run -p 8080:8080 plantuml/plantuml-server

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Diagram Types Quick Reference

UML Diagrams

Type	Keywords	Best For
Sequence	@startuml	Interactions, API flows, protocols
Use Case	@startuml	Requirements, user stories
Class	@startuml	OOP design, domain models
Activity	@startuml	Workflows, processes
Component	@startuml	System structure
Deployment	@startuml	Infrastructure, deployment
State	@startuml	State machines

Non-UML Diagrams

Type	Keywords	Best For
JSON	@startjson	JSON structure visualization
YAML	@startyaml	YAML structure visualization
Wireframe	@startsalt	UI mockups
Gantt	@startgantt	Project timelines
MindMap	@startmindmap	Hierarchical ideas
WBS	@startwbs	Work breakdown
ER	@startuml	Database schemas
C4	@startuml with C4 include	Software architecture

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Basic Syntax

All PlantUML diagrams are wrapped in start/end tags:

@startuml
' Your diagram code here
@enduml

Comments:

• Single line: ' This is a comment
• Block: /' This is a block comment '/

Title and captions:

@startuml
title My Diagram Title
caption This is a caption
header Page Header
footer Page Footer

' Diagram content
@enduml

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Quick Reference Card

Sequence

@startuml
participant A
participant B
A -> B: Message
A <-- B: Response
@enduml

Class

@startuml
class Name {
    - private
    + public
    + method()
}
A <|-- B : extends
A *-- B : contains
@enduml

Activity

@startuml
start
:Action;
if (condition?) then (yes)
    :True path;
else (no)
    :False path;
endif
stop
@enduml

State

@startuml
[*] --> State1
State1 --> State2 : event
State2 --> [*]
@enduml

Component

@startuml
[Component1] --> [Component2]
database DB
Component2 --> DB
@enduml

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References

For detailed syntax and complete examples, see:

Reference	Content	When to Load
sequence.md	Participants, arrows, activation, groups, notes	Creating sequence diagrams
class.md	Classes, visibility, relationships, cardinality	Creating class diagrams
activity.md	Conditions, swimlanes, fork/join	Creating activity diagrams
state-component.md	State machines, components, deployment	Creating state/component diagrams
c4.md	C4 context, container, component diagrams	Creating C4 architecture diagrams
special-diagrams.md	ER, JSON, MindMap, Gantt	Creating non-UML diagrams
styling-setup.md	Skinparams, themes, installation	Customizing diagrams, setting up PlantUML

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File Extensions

Extension	Description
.puml	Standard PlantUML file
.plantuml	Alternative extension
.pu	Short extension
.iuml	Include file

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Test Scenarios

Scenario 1: Creating a sequence diagram

Query: "Create a PlantUML sequence diagram for user authentication"

Expected: Skill activates, provides sequence syntax with participants, arrows, and alt/else blocks

Scenario 2: Creating a class diagram

Query: "Generate a PlantUML class diagram for an e-commerce domain"

Expected: Skill activates, provides class syntax with relationships and cardinality

Scenario 3: Creating a C4 diagram

Query: "Create a C4 container diagram in PlantUML"

Expected: Skill activates, directs to c4.md reference for includes and syntax

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Last Updated: 2025-12-28 PlantUML Version: 1.2024.6

Version History

• v1.1.0 (2025-12-28): Refactored to progressive disclosure - extracted content to references/
• v1.0.0 (2025-12-26): Initial release