# Sequence diagram generator — actors & messages, no upload

> Free sequence diagram generator: turn a few lines of Mermaid into a clean diagram of actors and messages. Live preview and SVG/PNG/PDF export, 100% on-device.

Turn a few lines of Mermaid into a clean sequence diagram of actors and the messages between them, with live preview and SVG/PNG/PDF export. It renders entirely on your device.

When you need to explain how systems talk — a login handshake, a webhook round-trip, a payment flow — a sequence diagram is the clearest picture. Writing it in Mermaid means you list the participants and the messages in order, and the timeline draws itself.

The expressive bits matter for real flows: loops for retries, alt blocks for branches, and notes to call out invariants like "nothing leaves the browser." Because it's text, updating the flow when the code changes is a one-line edit.

For decision logic use the Flowchart, for object structure use the Class diagram, or experiment across engines in the Playground.

## How to

1. **List participants.** Name the actors or systems involved.
2. **Add messages.** Write the calls and responses in order (A->>B: request).
3. **Annotate.** Add notes, loops, and activations as needed.
4. **Export.** Download the diagram as SVG, PNG, or PDF.

## FAQ

### What is a sequence diagram good for?

Showing how components interact over time — API calls, auth flows, message passing — as a top-to-bottom timeline of requests and responses between participants.

### Can I show loops, conditions, and notes?

Yes. Mermaid supports loops, alt/opt blocks, activations, and notes over participants, so you can capture real control flow, not just a happy path.

### How do I share it in docs?

Export SVG for crisp scaling in web docs, or PNG/PDF for slides and printed specs.

### Does my diagram get uploaded?

No. Rendering is local to your browser, so a flow that describes your internal architecture stays private.


## Related tools

- [Flowchart](https://www.safepaper.app/diagram/flowchart)
- [State diagram](https://www.safepaper.app/diagram/state-diagram)
- [Class diagram](https://www.safepaper.app/diagram/class-diagram)
- [Playground](https://www.safepaper.app/diagram/playground)

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Canonical HTML: https://www.safepaper.app/diagram/sequence-diagram
Markdown: https://www.safepaper.app/diagram/sequence-diagram.md

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