PlantUML Live Editor & Playground

Paste or type your PlantUML markup (starting with @startuml) into the editor on the left and the diagram renders instantly on the right — no installation, no Java, and no signup required. Start from a ready-made example or write your own sequence, class, use case, activity, or component diagram.

No. The PlantUML engine is compiled to JavaScript and runs entirely in your browser, including the Graphviz layout engine. Your diagram text never leaves your machine, so you can render diagrams privately and even offline once the page has loaded.

Yes. Paste the PlantUML markup an LLM or coding agent produced, render it immediately, and use the built-in AI assistant to validate and repair any broken syntax before you export or share it.

When your markup fails to render, the editor shows the engine's error message. Open the AI chat and it can explain the problem, validate a corrected version, and apply the fix directly in the editor.

Use the download button above the diagram to export your rendered PlantUML diagram as a PNG or SVG file that you can drop into docs, slides, or pull requests.

Click Share to generate a URL that encodes your current markup. Anyone who opens the link sees the same diagram in the editor, making it easy to collaborate or hand off a diagram.

PlantUML is an open-source tool that generates UML and many other diagrams from plain text. It supports sequence, class, use case, activity, component, state, and deployment diagrams, and is popular for documentation because diagrams live in version control as text.