Free tool

Sequence Builder

Build sequence diagrams from actors and messages, then export Mermaid.

Actors

Messages

Generated Mermaid

sequenceDiagram
  participant a1 as User
  participant a2 as Web
  participant a3 as API
  participant a4 as DB
  a1->a2: Open page
  a2->a3: GET /data
  a3->a4: SELECT …
  a4-->a3: rows
  a3-->a2: JSON