PlantUML Viewer

A free preview viewer to parse PUML code and render UML class and sequence diagrams instantly (WASM Engine powered). Supports direct image downloading. Works entirely in your browser, ensuring your source code is never sent to any external server.

Diagrams are rendered entirely in your browser using PlantUML WASM. Your diagram code is never sent to any external server. The PlantUML engine is downloaded once from CDN and cached by your browser.

PlantUML Input

Output

Initializing PlantUML Engine...

Failed to load CheerpJ runtime

First load takes 10-20 seconds. Subsequent visits will be much faster.

Guide & Terminology

What is the PlantUML Viewer?

A real-time diagram renderer that converts PlantUML text into visual diagrams (Sequence, Class, Activity, ER, Mind Map, etc.) entirely within your browser. No diagram data is ever sent to external servers.

How to use

Select a template or write your own PlantUML code in the editor.
The diagram is rendered automatically as you type (with a short delay).
Click Download to save the rendered diagram as PNG.

How it works

This tool uses PlantUML WASM powered by CheerpJ to run the official PlantUML Java engine directly in your browser via WebAssembly. The CheerpJ runtime (~10-20MB) is downloaded once from CDN and cached by your browser for fast subsequent loads.

Supported Diagram Types

Type	Syntax
Sequence	`@startuml ... @enduml`
Class	`@startuml ... @enduml`
Activity	`@startuml ... @enduml`
Use Case	`@startuml ... @enduml`
Component	`@startuml ... @enduml`
State	`@startuml ... @enduml`
ER	`@startuml ... @enduml`
Mind Map	`@startmindmap ... @endmindmap`

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