16 diagram types. No account. No server. Export SVG, PNG, or source to disk.
Write in whichever syntax you prefer — SeedUML auto-detects and renders.
PlantUML
Mermaid
Never used diagram-as-code? Here's why teams are switching from drag-and-drop.
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.
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.
No mouse, no palette, no alignment fiddling. Type A -> B: request and you have a sequence diagram. Modify 10 arrows in seconds, not minutes.
Everything stays in your browser. Download exactly what you need.
Download SVG, PNG (2x resolution), or source file (.puml / .mmd). Smart filenames with timestamps and diagram type.
No server, no cloud, no account, no tracking. Zero network requests during rendering. Nobody sees your diagram — not even us.
The entire rendering engine runs in your browser as a self-contained JavaScript bundle. No internet needed after the page loads.
Same rendering engine, installed as a Jira plugin. Diagrams appear directly in issue descriptions — not hidden in a panel.
Learn more — SeedUML for Jira