Text & Docs

PlantUML Editor

Edit PlantUML with templates and automatic PNG or SVG preview through the public PlantUML server. Copy source or preview links; see external rendering details.

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About this tool

Edit a single PlantUML diagram block and preview it as PNG or SVG. Templates help you start a diagram; paired start/end markers are checked before a preview request.

Preview rendering uses the public plantuml.com server. Your diagram source is encoded in the requested URL; encoding does not make it confidential.

Best use cases

  • Sketch a sequence diagram for a technical explanation.
  • Preview a template and share its rendered image URL.

How to use it

  1. Choose a template or paste one matching @start... / @end... diagram block.
  2. After a valid block is detected, wait for the automatic external preview. Choose PNG or SVG as needed.
  3. Copy the source or preview URL. Open the image to save it using your browser.

Two-message sequence diagram

Input

@startuml
Alice -> Bob: Hello
Bob --> Alice: Hi
@enduml

Preview shows Alice and Bob with a Hello arrow and a Hi return arrow. Copy this block into the editor; PNG and SVG render the same diagram.

Scope and limits

  • Previews one diagram block at a time. The local marker check is not a full PlantUML syntax validator.
  • A successful image load confirms delivery of an image, not that every PlantUML statement is correct; the server may return an error diagram.
  • Preview availability depends on the external service and your network. Avoid entering confidential diagram content in a public rendering workflow.

Data processing

Source editing is local. Automatic preview sends an encoded representation of the source in a URL to https://www.plantuml.com/plantuml. The browser and service may retain that URL. This page is not an entirely local renderer.

FAQ

Is preview rendering local?

No. The editor requests PNG or SVG from the public PlantUML server using an encoded source URL.

Why does a paired diagram block still show an error?

The local check covers block markers, not all PlantUML instructions. The remote renderer can still report a syntax error in its image.

Technical references

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