Online PlantUML & UML Editor
Type PlantUML code on the left and get a live preview on the right — sequence, class, use case, activity and state diagrams, mind maps and Gantt charts. The official PlantUML engine runs locally in your browser, so your diagrams never leave your machine.
How it works
- Pick a template (UML class, sequence, use case …) or paste your own @startuml … @enduml code
- The diagram re-renders as you type, without a round trip to any server
- Syntax problems are reported with the exact line number
- Export as SVG, PNG, JPG or PDF — or click the diagram to zoom fullscreen
Frequently asked questions
- Which UML and PlantUML diagram types are supported?
- UML sequence, class, activity, use case, state and component diagrams, plus mind maps and Gantt charts — the standard PlantUML syntax runs locally in the page.
- Is PlantUML the same as UML?
- PlantUML is a text-based way to draw UML (and other) diagrams: you describe the model in plain text and it renders the class, sequence, use case or activity diagram from it.
- Do I have to write @startuml / @enduml?
- No. If you paste only the diagram body, DocBox wraps it automatically before rendering.
- Is my diagram code sent to a server?
- No. The PlantUML engine is compiled to JavaScript and runs entirely inside the browser tab, so the source never leaves your device.
- Can I use it offline?
- Yes — after the first visit the app is cached as a PWA, so you can keep editing and exporting diagrams without a network connection.