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Carlo Sciolla b3cfafbf99
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2 months ago
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MELPA MELPA Stable CircleCI Coverage Status

PlantUML mode for Emacs

plantuml-mode in action

“Pummel me all you want,” I say. “Pummel me to death, in fact. My answers will not change.” The Invierno step back, frowning. “You must love her very much,” he says, not unkindly.”

from The Bitter Kingdom - Fire and Thorns #3

A PlantUML major mode for Emacs.


Make sure you have MELPA enabled in your emacs.d. Then, you can just

M-x package-install<RET>

Also, to enable preview you need to tell plantuml-mode where to locate the PlantUML JAR file. By default it will look for it in ~/plantuml.jar, but you can specify any location with:

M-x customize-variable<RET>

You can also download the latest version of PlantUML straight into plantuml-jar-path:

M-x plantuml-download-jar<RET>


  • Syntax highlight
  • Autocompletion
  • Preview of buffer or region

Enable the major mode

You can automatically enable plantuml-mode for files with extension .plantuml by adding the following to your .emacsrc:

;; Enable plantuml-mode for PlantUML files
(add-to-list 'auto-mode-alist '("\\.plantuml\\'" . plantuml-mode))

Of course, you can always enable manually the major mode by typing M-x plantuml-mode once in the desired PlantUML file buffer.


You can tell plantuml-mode to autocomplete the word before the cursor by typing M-x plantuml-complete-symbol. This will open a popup with all the available completions as found in the list of keywords given by running PlantUML with the -language flag.

To render the PlantUML diagram within Emacs, you can hit M-x plantuml-preview. This will run PlantUML and display the result in the *PLANTUML-Preview* buffer. The format used to render the diagram is automagically chosen from what’s supported by your Emacs. It will be one of the following, in order of preference:

  • SVG
  • PNG
  • Unicode ASCII art

The diagram will be either created from the selected region if one is available in the current buffer, or using the whole buffer otherwise.

If you want to force a specific output format, you can customize the variable plantuml-output-type to the value you prefer.

Default key bindings

The following shortcuts are enabled by default:

C-c C-c  plantuml-preview: renders a PlantUML diagram from the current buffer in the best supported format

C-u C-c C-c  plantuml-preview in other window

C-u C-u C-c C-c plantuml-preview in other frame

Integration with org-mode

You can use plantuml-mode to edit PlantUML source snippets within an org-mode document. To do so, you need to first register it with the plantuml language:

  'org-src-lang-modes '("plantuml" . plantuml))

Then you can edit a plantuml code block with plantuml-mode by hitting C-' while inside of the code block itself:

#+BEGIN_SRC plantuml
  <hit C-c ' here to open a plantuml-mode buffer>

When in the plantuml-mode buffer you can then hit again C-' to return to the original org-mode document.

Migration from puml-mode

If you were previously using puml-mode, you should change any reference to a puml-.. variable or function to its plantuml-.. counterpart. Most notably, puml-plantuml-jar-path is now just plantuml-jar-path.

Deprecation warning

If puml-mode is still being loaded by your Emacs, a Warning will be shown any time you open a PlantUML file. This is to remind you that you are running deprecated software. If you want to suppress the (intentionally) annoying warning, you can customize the variable plantuml-suppress-deprecation-warning.


Debug messages

As of v0.6.2 the following commands have been added to help resolving problems:


With debug enabled, the actual command used to invoke PlantUML is printed into a buffer called *PLANTUML Messages*. You can inspect that buffer to make sure that PlantUML is properly set up, or use it to supply extra information when opening issues.

Blank previews

If you are using SVG rendering and plantuml-preview shows you an empty buffer, chances are something is wrong with the PlantUML output. While inside the preview buffer, hit C-c C-c to switch to the textual mode and see if the output is valid SVG.


In order to contribute to plantuml-mode make sure to:

  • agree with the GPLv3+ licencing terms as they are mandated by Emacs
  • install cask
  • always test your code and run the full test suite with cask exec ert-runner (or just by make)


This project stemmed from the great work of Zhang Weize, and the current code still borrows a lot from it.

Thanks to Pavel G. Koukoushkin for implementing the preview functionality. Thanks to Raymond Huang for implementing the first drop of the indentation support.

Thanks to all the awesome contributors, you rock!

See also


Released under the terms of GPLv3 or (at your option) any later version. See LICENSE.txt.