PlantUML Anywhere

Preview local .puml/.plantuml files directly in the browser. No server, no upload, no install of Java/Graphviz.

PlantUML Anywhere renders .puml and .plantuml files the moment you open them with file:// — no Java, no Graphviz, no PlantUML server, and nothing is uploaded anywhere. Everything runs locally in your browser. HOW IT WORKS Open a local .puml or .plantuml file in Chrome or Brave and the diagram renders in place. Class diagrams, sequence diagrams, and everything else PlantUML supports. The extension uses @plantuml/core, the PlantUML engine compiled to JavaScript (TeaVM) with its Graphviz layout engine compiled to WebAssembly — no native binaries, no background service, no network calls. WHY THIS EXISTS Most PlantUML tools either require you to install Java and Graphviz locally, or send your diagram source to a remote rendering server. Neither is great if you just want to glance at a diagram, or if the file contains anything you'd rather not send elsewhere. This extension avoids both: the rendering engine ships inside the extension itself. PRIVACY Diagram source is read only from the local file you open, rendered entirely in your browser, and never leaves your machine. The extension makes no network requests. SETUP NOTE Browsers block extensions from reading file:// pages by default. After installing, a one-time setup page walks you through enabling "Allow access to file URLs" for this extension — without it, the preview won't appear. LIMITATIONS - No !include across multiple files (browser extensions can't read the filesystem beyond the open tab) - No bundled sprite libraries (AWS/Material/tupadr3 icon sets, etc.) - No export, snippets, or multi-page diagrams - Renders once per open/reload; no live preview while typing Source, issue tracker, and a VS Code extension built on the same rendering engine: https://github.com/t29mato/plantuml-anywhere