# Mermaid Sequence Diagram Syntax: A Practical Guide for API and Product Flows

> A deep, practical Mermaid sequence diagram guide with message types, activations, fragments, loops, and error handling. Includes patterns for APIs, webhooks, and async work.

Canonical: https://unidiagram.davidtran.dev/blog/mermaid-sequence-diagram-guide

- Published: 2025-12-31
- Reading time: 12 min
- Author: UniDiagram Team
- Tags: mermaid, sequence diagram, diagram as code, api documentation, architecture, engineering

A deep, practical Mermaid sequence diagram guide with message types, activations, fragments, loops, and error handling. Includes patterns for APIs, webhooks, and async work.

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