PlantUML Online — draft, preview, and export @startuml in the browser
PlantUML online is the practice of writing PlantUML syntax in a browser instead of installing the PlantUML jar, Java, or Graphviz locally. This page explains what PlantUML online means, when it is the right call, and how it compares to running PlantUML locally. If you already know you want an editor, jump straight in.
What's inside Beauty Diagram's PlantUML online editor
You get a live preview on one side, your @startuml source on the other, and the parser runs in the browser — no Java, no jar, no relay to plantuml.com.
Paste @startuml, render on every keystroke. No JRE, no PlantUML jar, no Graphviz dependency to install.
Beauty Diagram parses PlantUML directly — your @startuml is not relayed to plantuml.com or any third-party PlantUML server, so internal diagrams stay confidential.
Re-lays out activity, swimlane, sequence, class, and state diagrams so the main path, lanes, and branches read at a glance.
Full `if` / `elseif` / `else` / `fork` / `repeat` / `while` grammar plus `|lane|` and `|#color|lane|` swimlane syntax — rendered in a column-snap layout, not Graphviz dot output.
Switch between themes built for docs, slides, and reviews. The PlantUML source stays exactly as you wrote it.
Click any node or edge in the preview to change background, border, line color, width, and text color — no @startuml edits required.
Export SVG with fonts inlined. Pro adds 4× HD PNG sized for decks and printed handouts — watermark-free.
Sign in to save @startuml diagrams to the cloud and get a stable share link. Anonymous use stays free for preview, beautify, and export.
When using PlantUML online is the right call
PlantUML online wins whenever you value zero setup, shareability, and source confidentiality over scripting and offline access.
Open PlantUML online from any browser, type a few @startuml lines with `if` / `fork` / `repeat`, and see the activity diagram render instantly — no Java setup.
Save the @startuml source, send the share link, and the reviewer sees the rendered sequence diagram in their browser without installing PlantUML.
Use the one-click beautify pass on PlantUML activity, swimlane, sequence, class, or state diagrams, then export sleek SVG or HD PNG sized for docs and decks.
Paste a PlantUML block from a teammate, GitHub issue, or Slack thread and see it render without sending the source to the public plantuml.com server.
PlantUML online vs local PlantUML install
The two are complementary — most teams end up using both. Use local PlantUML when you need batch automation; use PlantUML online for everything else.
| Aspect | PlantUML online | Local PlantUML (jar + Java) |
|---|---|---|
| Setup time | Zero — open the page | Install Java + PlantUML jar (and often Graphviz) |
| Preview speed | Instant in the browser | Depends on Java startup + local toolchain |
| Source confidentiality | Parses in browser; source not sent to plantuml.com | Stays on your machine |
| Sharing the result | Stable share link, no install on receiver | Export file or push to repo |
| Batch / CI rendering | Manual per diagram | Scriptable, suited to CI |
| Cross-machine portability | Works on any browser | Re-install Java + jar on each machine |
| Beautified layout | One-click on Beauty Diagram | Manual tweak only |
How PlantUML online tools differ
"PlantUML online" is a category — several tools render @startuml in the browser, but they make very different trade-offs.
Renders exactly what the official PlantUML jar outputs. Source is sent to the public server for rendering — fine for public diagrams, less ideal for internal ones.
Convenient single-page UIs over the official renderer. Good for quick verification; minimal post-render polish.
Browser-side parser (no relay to plantuml.com), one-click beautify, presentation themes, and HD PNG export — for when the diagram is going somewhere people will read it.
For the editor itself see /plantuml-editor-online; for activity-specific cleanup see /plantuml-activity-beautifier.
Frequently asked questions
What does "PlantUML online" mean?
PlantUML online refers to writing PlantUML syntax in a browser instead of installing the PlantUML jar, Java, or Graphviz locally. You paste an @startuml block, the rendered diagram appears immediately, and you can export without any local setup.
Do I still need Java or the PlantUML jar?
No. Beauty Diagram parses PlantUML directly in our renderer — no Java runtime, no PlantUML jar, no Graphviz install. Open the page and paste.
Is my PlantUML source sent to a third-party server?
No. Many PlantUML online tools relay your source to the public plantuml.com server to render it. Beauty Diagram parses @startuml directly, so internal diagrams stay confidential — anonymous sessions never persist server-side either.
Is using PlantUML online free?
Yes. Anonymous preview, beautify, and SVG / PNG export on Beauty Diagram are free. An account is only required to save diagrams to the cloud and generate shareable links.
When should I use PlantUML online instead of a local install?
Use PlantUML online when you want to draft, preview, beautify, or export a diagram without setting up Java and the PlantUML jar — for example, drafting in a meeting, reviewing a teammate's @startuml block, or producing a polished diagram for a doc or slide. Use a local install when you need to render hundreds of diagrams in a CI pipeline or batch script.
Which PlantUML diagram types render online?
Activity, swimlane, sequence, class, and state all render live with theme-matched styling. Activity and swimlane have the most layout polish; component and other grammars also render with reasonable defaults.
Can I share a PlantUML diagram with a link?
Yes. After saving a diagram to a free or paid account, you get a stable share link. The recipient sees the rendered diagram in their browser with no install — no Java, no PlantUML jar.
Ready to use PlantUML online?
Open the PlantUML online editor in your browser. Paste @startuml, preview, beautify, and export — no Java, no jar.