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C4 Model

3 min readStatus:Seedling

Core Idea

The C4 Model is a hierarchical approach to architecture visualization that decomposes systems into Context, Container, Component, and Code—four progressively detailed levels that communicate architecture to different audiences.

Overview

Purpose: The C4 Model provides a simple, practical framework for visualizing software architecture through four hierarchical levels:

  • Each level serves a distinct purpose and audience
  • Created by Simon Brown
  • Addresses a fundamental challenge in architecture communication: how to show the right level of detail to the right stakeholders without overwhelming them or oversimplifying critical decisions

Four Hierarchical Levels:

Level 1: Context Diagrams:

  • Show the system boundary and its interactions with users and external systems
  • This highest-level view answers: “What does this system do and who uses it?”
  • Audience: All stakeholders—business users, executives, and technical teams alike
  • Value: Provides a shared understanding of system scope without implementation details

Level 2: Container Diagrams:

  • Decompose the system into major runtime components (applications, databases, microservices, file systems) and their communication patterns
  • Containers represent separately deployable or executable units
  • Reveals high-level technology choices (web application, mobile app, database, message queue)
  • Audience: Operations teams, security architects, and technical leadership
  • Value: Understanding deployment architecture

Level 3: Component Diagrams:

  • Zoom into a single container to show its internal structure
  • Show the major structural building blocks and their interactions
  • Components represent groupings of related functionality encapsulated behind well-defined interfaces (see Component-Definition)
  • Audience: Developers and architects working within a specific container
  • Value: Understanding internal organization and dependencies

Level 4: Code Diagrams:

  • Represent implementation details using class diagrams, entity-relationship diagrams, or other code-level visualizations
  • Optional in C4: Modern IDEs can often generate these views automatically
  • Audience: Developers working on specific components

C4 Model’s Strength - Progressive Disclosure:

  • Start at the context level with all stakeholders
  • Drill down to containers for technical discussions
  • Then to components for development planning
  • Each level maintains consistent notation (simple boxes and arrows)
  • Makes diagrams accessible without specialized training in UML or other complex notations

Why This Matters

Widespread Adoption Reasons: The C4 Model has gained widespread adoption because it balances simplicity with sufficient detail:

  • vs UML-Architecture-Diagrams: UML requires notation expertise; C4 diagrams are immediately readable by both technical and non-technical audiences
  • vs Informal “boxes and arrows”: C4 provides structure and consistency that prevents ambiguity

Communication Benefits: Architects adopting C4 can communicate architecture decisions at the appropriate level of abstraction for each audience:

  • Executives: See context diagrams
  • Operations teams: See container diagrams
  • Development teams: See component diagrams
  • Results:
    • Targeted communication reduces confusion
    • Accelerates onboarding
    • Ensures architectural intent is preserved during implementation

Sources

Note

This content was drafted with assistance from AI tools for research, organization, and initial content generation. All final content has been reviewed, fact-checked, and edited by the author to ensure accuracy and alignment with the author’s intentions and perspective.

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