Option: Diagrams extension

With the extension option Diagrams extension you can embed diagrams in your AsciiDoc files as text based descriptions using the Kroki.io online service.

The Kroki server (default or custom) converts the text to its corresponding image. You do not need any other software installed on your machine or browser.

On this page you will find:

  • how to configure the extension option Diagrams extension

  • an example

  • a try-it-yourself example.

To learn more about diagrams from text based descriptions and "diagrams like code", visit kroki.io.

Diagrams extension options

There are two options for the diagrams extension:

  • Enable the diagrams extension

  • The Server URL

Enable the diagrams extension

Enable or disable the diagrams extension with this option.

When enabled, the diagrams extension is sending the text diagrams to an instance of Kroki to display them as images in the preview. Kroki is a free open-source project.

When you enable the diagrams extension without changing the default server URL, you agree to the diagrams extension sending your diagrams to the free public cloud instance kroki.io for conversion.

Server URL

The Server URL defines the URL of a Kroki diagram server.

By default, the diagrams extension sends your diagrams to the free public cloud instance kroki.io, but you can install Kroki on your own infrastructure. Once you’ve installed Kroki, make sure to update the server URL to point to your instance.

Learn more about installing Kroki at kroki.io


The diagrams extension allows you to take further advantage of the "docs like code" approach for faster and more effective manually created diagrams from text.

Diagrams from text in general enables further documentation automation.

Benefits of the diagrams extension

  • Manage diagram assets related to the document, with the documents

  • Manage change quickly, as the diagram can be updated by editing text

  • Accept changes faster, as for many small diagrams, the change is evident in the text and does not require the rendered image to be present

  • More expressive documents, as writers are able to make quick diagrams to convey concepts that would otherwise take too much time

  • Less storage volume, as the images are only present in the final output

  • Faster git operations, as it is not managing large numbers of image artifacts that increase the size of the repository

Benefits of installing Kroki

The benefits of running Kroki locally, or installing it on your own infrastructure are:

  • Diagram conversion traffic remains inside your organization

  • Depending on the diagram generator used, you may standardise diagram themes for consistency across your organization without changing source diagrams

Learn more about installing Kroki at kroki.io

Example diagram

Below is a three-step process diagram using the GraphViz dot language.

three step process
Figure 1. Three-step process

The AsciiDoc and embedded diagram text to produce the above diagram is below.

digraph { rankdir=LR a -> b -> c}

For more information about embedding diagrams as text and GraphViz diagrams, visit kroki.io and graphviz.org.

Try it yourself

Below is an example diagram showing communication between the Diagrams extension and the Kroki.io server set by the Server URL in Extension Options.

You’ll create the AsciiDoc file that both holds and displays the diagram when viewed with the Asciidoctor Browser Extension.

The diagram below uses the PlantUML diagram generator. To learn more about embedding diagrams, other diagram languages and PlantUML, visit kroki.io and plantuml.com.

diagrams extension sequence
Figure 2. Diagrams extension sequence

To create the above diagram after installing the Asciidoctor Browser Extension, do the following:

  1. Create a file "diagram-extension-example.adoc" with the following contents:

    = Diagrams extension example with Kroki.io
    The sequence diagram is below:
    entity "Local or remote file" as file
    box Browser #white
    participant Browser as browser
    participant "Asciidoctor\nBrowser Extension" as extension
    box "Kroki Server" #white
    participant "Kroki Gateway" as kroki
    participant "Diagram generator" as generator
    end box
    file -> browser : AsciiDoc
    browser -> extension : AsciiDoc
    activate extension
    extension -> kroki : encoded diagram text
    kroki -> generator : diagram text
    kroki <- generator : image
    extension <- kroki : image
    browser <- extension : HTML5
    deactivate extension
  2. Enable the Diagrams extension with the default Server URL from the extension options. For help enabling and disabling the Diagrams extension, see the Extension Options page.

  3. Open or reload the above file in the browser to see the diagram.

  4. Modify the diagram text in the AsciiDoc and reload the page to see your updated diagram.

  5. Disable the Diagrams extension.

    Disable the Diagrams extension to stop communication with the Server URL.