5 PlantUML Diagram Templates (Copy-Paste Ready)

Same as the intro post — AI-assisted sample. The templates themselves are ready to run; feel free to rewrite the prose.

1. Sequence diagram

@startuml
title User login flow
actor User
participant "Frontend" as FE
participant "API Gateway" as GW
participant "Auth Service" as Auth
participant "User Service" as UserSvc

User -> FE: enter credentials
FE -> GW: POST /login
GW -> Auth: validate token
Auth -> UserSvc: query user
UserSvc --> Auth: return user data
Auth --> GW: token valid
GW --> FE: 200 OK + JWT
FE --> User: redirect home
@enduml

Tip: alias long participant names with as; -> is a solid arrow, --> is a dashed reply.

2. Class diagram

@startuml
class User {
  -id: Long
  -email: String
  -createdAt: DateTime
  +login(): boolean
  +logout(): void
}

class Order {
  -id: Long
  -userId: Long
  -total: BigDecimal
  -status: OrderStatus
  +pay(): void
  +cancel(): void
}

User "1" --> "*" Order : places
Order ..> User : belongs to
@enduml

Tip: - / + / # mean private / public / protected; --> is association, <|-- inheritance, *-- composition, o-- aggregation, ..> dependency.

3. Usecase diagram

@startuml
left to right direction
actor "User" as U
actor "Admin" as A

rectangle System {
  U --> (Browse products)
  U --> (Place order)
  U --> (View orders)
  (Place order) ..> (Pay) : include
  A --> (Manage products)
  A --> (Process refunds)
}
@enduml

Tip: include means a mandatory sub-usecase, extend means an optional one.

4. State diagram

@startuml
title Order state machine
[*] --> PendingPayment : order created
PendingPayment --> Paid : payment ok
PendingPayment --> Cancelled : user cancel / timeout
Paid --> Shipped : merchant ships
Shipped --> Delivered : user confirms
Delivered --> [*]
Cancelled --> [*]
@enduml

Tip: use [*] for start/end states; add notes with note right of StateName : text.

5. Activity diagram

@startuml
title Article publish flow
start
:write draft;
:spell check;
if (passed?) then (yes)
  :save draft;
  :notify reviewer;
else (no)
  :show errors;
  stop
endif
:reviewer approves?;
if (approved?) then (yes)
  :publish article;
else (no)
  :send back;
  stop
endif
stop
@enduml

Tip: if (...) then (...) else (...) endif is the branch construct; switch / while / repeat all exist.

How to preview these

This site’s online editor (coming soon): paste and preview live on the right
VSCode: install the PlantUML extension, press Alt+D to preview
CLI: plantuml -tpng diagram.puml produces a PNG

Need more templates (ER, component, mind map)? Leave a comment.