Edit any supported diagram type
Use the same source and preview workspace for sequence, class, activity, use case, state, component, ER, object, deployment, and other PlantUML diagrams.
PlantUML Online Editor
Edit any PlantUML diagram online, choose ready-to-use templates, preview changes as you type, and download PNG or SVG without installing Java or Graphviz.
PlantUML editor and live preview
Choose a diagram template or paste existing PlantUML source, then check the rendered result beside the code.
Template
Diagram preview
Use this editor for quick previews and exports across diagram types. Open the full editor for AI generation, syntax repair, sharing, and saved projects.
One editor for every PlantUML diagram
The general editor is for PlantUML source that is not limited to one diagram type. Start from a template, inspect existing code, or prepare a file for export.
Multiple diagram templates
Start with sequence, class, activity, use case, state, component, ER, and other PlantUML examples from one selector.
Live diagram preview
Compare the source and rendered output while you edit, so missing labels and syntax problems are easier to notice.
PNG and SVG downloads
Download a bitmap for slides and tickets, or choose SVG when documentation needs sharp text at any size.
No local setup
Preview PlantUML in the browser without installing Java, Graphviz, a desktop application, or an IDE extension.
How to use the PlantUML online editor
Use the general editor when you already have PlantUML source or want to compare several diagram types before choosing a focused tool.
- 01
Choose the template closest to the diagram you want to create, or paste existing PlantUML source.
- 02
Edit names, relationships, messages, and styling directives in the source panel.
- 03
Check the live preview and correct any syntax or labeling problems.
- 04
Download PNG or SVG, or continue in the full editor when the diagram needs AI assistance or project history.
What the general PlantUML editor is for
This page covers the type-independent PlantUML workflow. Focused diagram pages remain available when you need syntax guidance and examples for a specific model.
Use it as a PlantUML viewer
Paste PlantUML from documentation, a repository, or a code review to inspect the rendered result without changing your local environment.
Move to a focused diagram tool
Open a diagram-specific editor when you want a targeted starting template, dedicated syntax explanations, practical examples, and questions for that model.
Continue beyond a quick preview
Send the source to the full OnUML editor when you need AI generation, syntax repair, saved projects, sharing, or a longer editing session.
A PlantUML example you can edit
The default sequence diagram demonstrates the complete workflow: edit readable text, verify the preview, then download the format you need.
@startuml
actor User
participant "OnUML Editor" as Editor
participant "PlantUML Server" as Server
User -> Editor: Write PlantUML code
Editor -> Server: Render diagram preview
Server --> Editor: Return diagram
Editor --> User: Show live preview
@endumlChoose a focused PlantUML workflow
Use a diagram-specific editor for targeted guidance, browse the complete tool directory, or open a converter when the output format is already decided.
PlantUML Tools for Every Diagram Task
Compare every PlantUML diagram editor and export tool available on OnUML.
Open toolSequence Diagram
Model participants, messages, conditions, loops, and service interactions.
Open toolClass Diagram
Describe classes, members, interfaces, inheritance, and object relationships.
Open toolActivity Diagram
Map actions, decisions, loops, parallel work, and swimlane ownership.
Open toolPlantUML to SVG Converter
Convert existing PlantUML source into a scalable SVG file.
Open toolPlantUML to PNG Converter
Convert existing PlantUML source into a PNG for documents and presentations.
Open toolWhy keep a general PlantUML editor
Specific diagram pages answer focused questions. This page remains the direct workspace for users who only need to open, inspect, edit, or export arbitrary PlantUML source.
Start without classifying the diagram
Open the source first, then choose a focused page only if the diagram needs type-specific guidance.
Keep source and output together
Review the text and rendered result in one workspace before copying the code or downloading an image.
Use the right next step
Move from a quick preview to a focused diagram tool, a format converter, or the full editor without restarting the work.
Frequently Asked Questions
What is a PlantUML online editor?
It is a browser-based workspace for writing or pasting PlantUML source, previewing the rendered diagram, and downloading PNG or SVG without a local PlantUML installation.
Which PlantUML diagram types can I edit here?
You can edit any diagram supported by the configured PlantUML renderer, including sequence, class, activity, use case, state, component, ER, object, and deployment diagrams.
Can I use this page as a PlantUML viewer?
Yes. Paste existing PlantUML source into the editor and use the preview panel to inspect the rendered result.
Can I download both PNG and SVG?
Yes. PNG is useful for slides, tickets, and quick sharing. SVG is better for scalable documentation and web content.
Do I need to install Java or Graphviz?
No. The preview and export workflow runs online, so you do not need to install Java, Graphviz, or a local IDE extension.
How is this different from the sequence or class diagram pages?
This page accepts arbitrary PlantUML source. The focused pages provide a diagram-specific template, syntax guidance, examples, and FAQs for one modeling task.
When should I open the full OnUML editor?
Use the full editor when you need AI generation, syntax repair, sharing, saved projects, or a longer multi-format diagram workflow.
Need more than a quick PlantUML preview?
Continue in the full OnUML editor for AI generation, syntax repair, sharing, saved projects, and multi-format diagram work.