Atlas PlantUML

Interactive preview for PlantUML diagrams in Visual Studio Code: smooth pan and zoom, dark mode, layout selector, search, minimap, export and an Arrange tool that looks for a more readable order of your declarations.

Credits

Atlas PlantUML is an independent derivative of Plan UML by Justus Karlsson, released under the MIT License. It keeps Plan UML's interactive preview and Journeys panel, rewritten in TypeScript, and adds the features listed below. It is not affiliated with or endorsed by Justus Karlsson.

It also includes, unmodified:

• PlantUML 1.2025.10 by Arnaud Roques, under the GNU GPL v3 or later. The extension runs it as a separate program.
• The PlantUML syntax grammar from PlantUML for VS Code by jebbs, under the MIT License.

See THIRD_PARTY_NOTICES.md for the full notices.

Features

• Live preview that opens with any .puml file and re-renders when the diagram changes.
• Smooth pan and zoom for large diagrams, with animated wheel zoom.
• Dark mode that recolors the diagram without changing its layout.
• Layout selector: Default, Polyline, Curves, Left to right, LR + polyline, ELK and Smetana, without editing the file.
• Search classes and packages with Ctrl+F, and a minimap to move around.
• Relations: click a class to dim everything that is not connected to it.
• Go to source: double-click a class, package or arrow to open its line.
• Export to PNG (up to 2x) or SVG.
• Arrange: tries other orders of the top-level declarations, previews the ones with fewer arrow crossings, and applies the one you pick (undo with Ctrl+Z).
• Syntax errors in the Problems panel.
• Preview + Source editor, from "Reopen Editor With...".
• Journeys panel from Plan UML, hidden by default.
• Syntax highlighting for .puml, .pu, .plantuml, .iuml, .wsd and plantuml code blocks in Markdown.

Requirements

• Java 8 or later on your PATH. PlantUML is bundled and runs locally: your diagrams never leave your machine.
• Graphviz for the Default, Polyline, Curves and Left to right layouts. Without it, use the ELK or Smetana layouts, which need nothing else.

Getting started

1. Install Atlas PlantUML from the Visual Studio Code Marketplace.
2. Open a .puml file: the preview opens on its own.
3. To see the code next to it, use "Reopen Editor With..." and pick Atlas PlantUML Preview + Source.

Commands, in the Command Palette under Atlas PlantUML: Open Atlas PlantUML Preview, Close All Previews and Reload All Previews.

Migrating from the previous build

If you installed the earlier internal build of this extension, uninstall it first: Atlas PlantUML uses a new extension ID, so VS Code treats it as a different extension. If the original Plan UML is installed, uninstall it too so only one preview opens .puml files.

Contributing

Read AGENTS.md before changing anything. Every change must pass pnpm run verify.

License

The extension's own code is under the MIT License, which keeps Justus Karlsson's original copyright notice. The bundled PlantUML jar stays under the GNU GPL v3 or later, and its source code is available at plantuml/plantuml, tag v1.2025.10. Third-party components and their licenses are listed in THIRD_PARTY_NOTICES.md.