Free UML Diagram Tool — Sequence, Class & Activity | nopa

Productivity

Draw a UML diagram

Sketch a sequence diagram here and download a PNG — class boxes, activity flows, UML templates and SVG export open in the full Board in the desktop.

Try it now — no account needed

Save and continue on the desktop

Download or copy your result here first. Continue in nopa to save to Files or use more features.

  • Whiteboard with snap arrows, stickies, and shapes — saved locally
  • Results saved to Files automatically
  • Every tool in one place — no new tabs
Open the free desktop

After you download — continue on the desktop for Files or the full app.

UML shapes developers use

Class compartments, lifelines, actors, and state nodes — plus arrows with labels for messages and associations.

One-click templates

Insert a login sequence (User → API → DB), a two-class diagram, or an activity flow with decisions — then customize in place.

Snap connectors

Draw arrows between classes and lifelines. Endpoints snap to edges and move when you drag shapes.

Local export

Download PNG on this page or open Board in nopa for autosave, SVG/JSON export, and Files integration.

Related apps

Questions

Which UML diagram types are supported?

Sequence, class, and activity templates plus manual tools for classes, lifelines, actors, and states.

Is it better than BPMN here?

UML targets software design (classes, sequences). BPMN targets business processes — both live in Board.

Where is my diagram stored?

In nopa, boards are stored in your browser on your device.

Can I continue from this page?

Yes — download PNG or click Continue in nopa to load a sequence template in the full Board app.