PlantUML Styles and Options

The PlantUML backend supports several layout and styling options that control diagram direction, legend visibility, and overall visual appearance.

See the C4-PlantUML docs for additional information.

Layout Options

Layout behavior is configured via the LayoutOptions builder:

from c4.renderers.plantuml import LayoutOptions

layout_options = (
    LayoutOptions()
    .layout_landscape()   # Horizontal layout
    .show_legend()        # Display legend
)

You can pass layout_options to PlantUMLRenderer.

See the Layout Options reference section for the complete list of available methods and configuration options.

C4 Visual Styles

Starting July 2025, the official c4model.com website introduced a refreshed visual style for C4 diagrams.

The PlantUML renderer supports both:

• Classic style (default)
• New C4 style (opt-in)

Classic Style (Default)

from c4 import *
from c4.renderers.plantuml import PlantUMLRenderer, LocalPlantUMLBackend
from c4.renderers.plantuml import LayoutOptions


with ComponentDiagram() as diagram:
    admin = Person("Administrator")

    with SystemBoundary("Sample"):
        with ContainerBoundary(
            "Web Application",
            "Allows users to compare\nmultiple Twitter timelines",
        ) as web_app:
            twitter_facade = Component("Twitter Facade")

    twitter = System("Twitter")

    admin >> RelRight("Uses", technology="HTTPS") >> web_app
    twitter_facade >> RelRight("Gets tweets from", technology="HTTPS") >> twitter

    layout_options = LayoutOptions().layout_landscape().show_legend()

    renderer = PlantUMLRenderer(
        backend=LocalPlantUMLBackend(),
        layout_options=layout_options,
    )


renderer.render_file(
    diagram,
    output_path="diagram.png",
    format=PNG,
)

This produces the classic C4 visual style:

diagram.png

New C4 Style

To enable the updated visual style, pass use_new_c4_style=True to PlantUMLRenderer:

from c4 import *
from c4.renderers.plantuml import PlantUMLRenderer, LocalPlantUMLBackend
from c4.renderers.plantuml import LayoutOptions


with ComponentDiagram() as diagram:
    admin = Person("Administrator")

    with SystemBoundary("Sample"):
        with ContainerBoundary(
            "Web Application",
            "Allows users to compare\nmultiple Twitter timelines",
        ) as web_app:
            twitter_facade = Component("Twitter Facade")

    twitter = System("Twitter")

    admin >> RelRight("Uses", technology="HTTPS") >> web_app
    twitter_facade >> RelRight("Gets tweets from", technology="HTTPS") >> twitter

    layout_options = LayoutOptions().layout_landscape().show_legend()

    renderer = PlantUMLRenderer(
        backend=LocalPlantUMLBackend(),
        layout_options=layout_options,
        use_new_c4_style=True,
    )


renderer.render_file(
    diagram,
    output_path="diagram.png",
    format=PNG,
)

This produces the updated C4 visual style:

diagram.png