How to create a Use Case diagram in PlantUML

1. Try it in the browser

You can render PlantUML diagrams instantly in your browser with the PlantUML Playground — no Java or server install required. The examples below can be pasted directly into it.

2. Define the diagram

A use case diagram declares actors with actor Name and use cases with parentheses, either as Name as (Alias) or with a shorthand (Use case text). Connect an actor to a use case with a plain line -- to show it participates in that use case.

@startuml
actor Customer
actor "Support Agent" as Agent
usecase "Place Order" as UC1
usecase "Track Shipment" as UC2
usecase "Request Refund" as UC3
Customer -- UC1
Customer -- UC2
Customer -- UC3
Agent -- UC3
@enduml

Here, Customer can place an order, track a shipment, or request a refund, and a Support Agent also participates in handling refunds.

3. Include, extend, and generalization

Use case diagrams support a few special relationships beyond a plain association:

Relationship	Syntax	Meaning
Association	`Actor -- (Use case)`	The actor participates in / triggers the use case
Include	`(A) ..> (B) : include`	Use case A always performs the steps of use case B
Extend	`(A) ..> (B) : extend`	Use case A optionally adds behavior to use case B under some condition
Generalization	`(A) <\|-- (B)`	Use case or actor B is a specialized variant of A (empty triangle arrowhead)

4. System boundaries

Wrap related use cases in a rectangle "System name" { ... } block to draw a labeled boundary box around them, separating what the actors do from what the system provides:

@startuml
left to right direction
actor Customer
rectangle "Online Store" {
  usecase "Browse Catalog" as UC1
  usecase "Add to Cart" as UC2
  usecase "Checkout" as UC3
  usecase "Process Payment" as UC4
  UC3 ..> UC4 : include
}
Customer -- UC1
Customer -- UC2
Customer -- UC3
@enduml

The left to right direction statement is commonly used for use case diagrams so actors sit to the side of the system boundary rather than above it.

5. Render the diagram

Once you have defined the diagram, you can render it on your webpage with the @plantuml/core browser engine (the same one that powers this site's live editor), or by sending the markup to a PlantUML rendering server that returns an SVG image, the same way as shown on the PlantUML sequence diagram page.

You can use this PlantUML Playground Link to explore that particular example.