Mermaid Sequence Diagram

Illustrate interactions between objects over time with sequence diagrams. Model message flows and communication in your systems.

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Quick Syntax Reference

Key syntax for creating sequence diagrams.

ParticipantsDefine actors and objects

sequenceDiagram
  actor User
  participant A
  participant B as "Service B"

MessagesSend messages between participants

A ->> B : Synchronous
A -->> B : Asynchronous
A ->> A : Self message
A ->>+ B : Activate
A -->>- B : Deactivate

LoopsRepeat message sequences

loop Every minute
  A ->> B : Ping
  B -->> A : Pong
end

AlternativesConditional flows

alt Success
  A ->> B : Data
else Error
  A ->> B : Error
end

NotesAdd annotations

Note over A,B : Shared note
Note left of A : Left note
Note right of B : Right note

ActivationLifeline activation

A ->>+ B : Activate B
B ->>+ C : Activate C
C -->>- B : Return
B -->>- A : Return

Sequence diagrams illustrate how objects interact in a particular scenario.

Document API calls and responses.

Show interactions between microservices.

Visualize specific user scenarios.

Design and document communication protocols.

Trace and analyze system interactions.

Review and discuss system designs.