PlantUML Live Editor & Playground
PlantUML source
Auto-renders as you type
Free PlantUML live editor in your browser
Write PlantUML source and see a live diagram preview, or switch between Code and Preview on your phone. This PlantUML editor runs entirely in your browser — no Java, no server, and no signup — so you can prototype sequence diagrams, class diagrams, use case diagrams, activity diagrams, and component diagrams in seconds. Start from a ready-made example or paste your own @startuml markup to render a UML diagram online. The engine loads on your first visit; if loading fails, use Retry loading without losing your source.
Fix and validate AI-generated PlantUML
Large language models and coding agents often emit PlantUML with small syntax errors. Paste diagram code from ChatGPT or any AI agent and the built-in AI assistant will validate it, explain what broke, and apply a corrected version directly in the editor — so you can fix a PlantUML syntax error without hunting through the docs. Rendering runs locally; optional AI assistance sends your source to the AI service.
Export and share your diagrams
Use Export to download an up-to-date diagram as PNG or SVG for docs, slides, and pull requests, or generate a shareable link that reopens the exact diagram in the editor. Exports include the full diagram regardless of preview zoom or pan. Prefer a different notation? Try the MermaidJS playground or the Graphviz editor.
