Write PlantUML in your browser, with nothing to install
PlantUML describes structural diagrams — classes, components, deployments — as text. You can write and render them here without installing Java or a drawing tool.
How to write it
Class diagram
```plantuml
@startuml
class Document {
+title: string
+save(): void
}
class Revision
Document "1" o-- "*" Revision
@enduml
```Everything between @startuml and @enduml is one diagram. o-- is aggregation and "1" / "*" are multiplicities. Attributes and methods go inside the class braces.
Sequence diagram
```plantuml
@startuml
actor User
User -> Editor: write the body
Editor -> Storage: keep a draft
Storage --> Editor: saved at
@enduml
```-> is a solid call and --> a dashed reply. Only names declared with actor are drawn as stick figures; the rest are drawn as boxes.
What this editor gives you
The diagram lives in the document
A diagram is a plantuml code block inside your Markdown, kept in the same file as the prose around it.
Nothing leaves without your say-so
PlantUML is rendered by an external server (plantuml.com). You are asked before the diagram code is sent, so the decision stays yours.
Still plain Markdown when you leave
The file is ordinary Markdown. Run it through your own PlantUML installation later and you get the same diagram.
Frequently asked questions
Do I need Java or a drawing tool?
No. A browser is enough.
Where is the diagram rendered?
On an external server (plantuml.com). Because the diagram code travels over the internet, you are asked to confirm before anything is sent, and nothing is sent until you do.
Should I use PlantUML or Mermaid?
PlantUML is the better fit when the structure has to be precise, such as class or deployment diagrams. Mermaid is quicker for flows and conversations. Both can sit in the same document.
You can try this syntax right now.
Open the editor