PlantUML & Mermaid diagrams, instantly.
In your browser. In your Jira. Free.

16 diagram types. No account. No server. Export SVG, PNG, or source to disk.

Try the Playground Install on Jira
auth-flow.puml PlantUML
Rendering...
rendered live by SeedUML — the same engine powering the playground
Zero network requests 16 diagram types 887 unit tests Works offline Source on GitLab →

PlantUML + Mermaid. 16 types. One editor.

Write in whichever syntax you prefer — SeedUML auto-detects and renders.

PlantUML

Mermaid

Text in, diagrams out

Never used diagram-as-code? Here's why teams are switching from drag-and-drop.

AI-native

AI-native

Paste a sequence diagram into ChatGPT and say "add error handling." It works — because your diagram is text, not pixels. Try that with a PNG from a visual editor.

Version-control friendly

Version-control friendly

Diagram source is plain text. It diffs, merges, and lives in your Git history alongside the code it documents. Review diagram changes in a pull request just like code.

Faster than dragging

Faster than dragging

No mouse, no palette, no alignment fiddling. Type A -> B: request and you have a sequence diagram. Modify 10 arrows in seconds, not minutes.

"Add error handling to this diagram" — any LLM can do this because it's just text
@startuml Client -> API: POST /order API -> DB: Insert order DB --> API: OK API --> Client: 201 Created @enduml

Your diagrams. Your files. Your disk.

Everything stays in your browser. Download exactly what you need.

Export anything

Download SVG, PNG (2x resolution), or source file (.puml / .mmd). Smart filenames with timestamps and diagram type.

100% private

No server, no cloud, no account, no tracking. Zero network requests during rendering. Nobody sees your diagram — not even us.

Works offline

The entire rendering engine runs in your browser as a self-contained JavaScript bundle. No internet needed after the page loads.

Using Jira? Get diagrams inline in your issues.

Same rendering engine, installed as a Jira plugin. Diagrams appear directly in issue descriptions — not hidden in a panel.

Learn more — SeedUML for Jira