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Sequence Diagram Generator

Write one message per line and see who talks to whom, in order, as a sequence diagram.

Processed locally in your browser

Options
One message per line: "Sender -> Receiver: text". Use "-->" for a dashed reply. Or paste Mermaid "sequenceDiagram" code.0 chars · 0 lines
The result will appear here.

What is Sequence Diagram Generator?

A sequence diagram shows how participants (users, services, databases) exchange messages over time. It is the standard way to document an API call, a login flow or a protocol handshake.

In quick mode you only write "Sender -> Receiver: message" per line, and "-->" for a dashed reply. The tool declares the participants in order of first appearance, converts arrows to the Mermaid syntax, escapes characters that would break the parser and shows the generated Mermaid code next to the diagram. You can also paste your own sequenceDiagram code with loops, alternatives and notes.

How does it work?

  1. Write messages as "Sender -> Receiver: text" (one per line); use "-->" for replies.
  2. Tick "Number the messages" to add autonumbering, and choose whether participants repeat at the bottom.
  3. Pick a theme and check the diagram and the generated "Mermaid code" panel.
  4. Export SVG or PNG, or copy the Mermaid code into your docs.

Common use cases

  • Documenting a REST API call or an OAuth login flow between browser, server and database.
  • Explaining a microservice interaction in a design review.
  • Sketching a protocol handshake for a specification.
  • Preparing a support or incident write-up that shows the order of events.

Examples

Try this input in the tool above:

Browser -> Server: GET /login
Server -> Database: Find user
Database --> Server: User record
Server --> Browser: 200 OK + session cookie
Browser -> Server: GET /dashboard
Server --> Browser: Dashboard page

Privacy

Sequence Diagram Generator runs entirely in your browser. The text or files you provide are processed on your device and are not uploaded, logged or stored on our servers.

Limitations

The quick outline supports plain messages and reply arrows only. Loops, alt/opt blocks, activations and notes require Mermaid sequenceDiagram code. Participant names with spaces are shown as aliases.

Frequently asked questions

How do I show a reply message?

Use a double dash arrow: "Server --> Browser: 200 OK" draws a dashed line, while "Browser -> Server: GET /" draws a solid one with an arrowhead.

Can participants have names with spaces?

Yes. Names such as "Payment service" are declared with a generated id and shown with their full name in the diagram.

Can I add loops or alternatives?

Yes, in Mermaid code mode. Paste code starting with sequenceDiagram and use loop, alt/else, opt, par and Note over; the autonumber option still applies.

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