Basic PlantUML Syntax

Every PlantUML file requires a start and end command. These will be the first and last lines of your code. X number of them use the same command a few of the supported non-UML diagrams have their own start and end commands. The table below shows the commands for each diagram.

Diagram Type	Start Command	End Command
Sequence Diagram	@startuml	@enduml
Use Case Diagram	@startuml	@enduml
Class Diagram	@startuml	@enduml
Object Diagram	@startuml	@enduml
Activity Diagram	@startuml	@enduml
Component Diagram	@startuml	@enduml
Deployment Diagram	@startuml	@enduml
State Diagram	@startuml	@enduml
Network Diagram	@startuml	@enduml
Salt or Wireframe	@startsalt	@endsalt
Archimate Diagram	@startuml	@enduml
Gantt Chart	@startgantt	@endgantt
MindMap	@startmindmap	@endmindmap
Work Breakdown Structure	@startwbs	@endwbs
JSON	@startjson	@endjson
YAML	@startyaml	@endyaml

Example: Basic PlantUML File

@startuml



@enduml

Commenting Code

Code comments are ignored by the program. Use them to plan or explain to the next person (future you) what your code is doing. To comment in PlantUML, put a single quote at the beginning of the line.

Example: Commenting Code

@startuml
'The above line is required for most PlantUML files.

'This line will be ignored by PlantUML.

'The below line is required for most PlantUML files.
@enduml

Mixing Diagrams and Syntax Errors

PlantUML is used to make several types of diagrams. As shown above, many of them are enclosed within the same @startuml and @enduml lines. Because of this, PlantUML determines the type of diagram based on the body of your code. If you mix code from multiple types of diagrams, you may only receive a syntax error. If you continually get a syntax error and know there is nothing wrong with the particular line throwing the error, ensure you aren't accidentally using syntax from another type of diagram.

We will show this in the following three examples. The first two sets of code and images will make a proper diagram. The third set will combine the first two and throw a syntax error.

Example: Functional Sequence Diagram

@startuml

'The following code is used in a sequence diagram.

participant Sean
participant Maria

Sean  ->  Maria 
Sean  <-- Maria

@enduml

Sequence Diagram

Example: Functional Use Case Diagram

@startuml

'The following code is used in a use case diagram.

(Door)

:Sean:

Sean -> Door

@enduml

Use Case Diagram

Example: Broken Diagram

@startuml

'The following code is used in a sequence diagram.

participant Sean
participant Maria

Sean  ->  Maria 
Sean  <-- Maria

'The following code is used in a use case diagram.
'Because of the mixed code. PlantUML will throw an error on line 14.

(Door)

:Sean:

Sean -> Door

@enduml

Broken Diagram