C4 Model
The C4 Model is a lean approach to software architecture diagramming created by Simon Brown. It provides a standardised way to visualise software systems at four levels of abstraction: Context (showing the system and its relationships to users and other systems), Container (showing the high-level technical building blocks like web servers, databases, and applications), Component (showing the internal structure of individual containers), and Code (showing how components are implemented, typically through class diagrams). For non-technical readers, the C4 Model is like having different zoom levels on a map. At the highest level, you see where a city sits relative to other cities (Context). Zoom in and you see the major districts and transport links (Container). Zoom further to see individual buildings and streets (Component). Finally, you can examine the floor plan of a specific building (Code). Each level serves different audiences and discussions. The model addresses a common problem in software development: architects often create diagrams that are either too abstract to be useful or too detailed to understand. The C4 Model provides just enough structure to communicate clearly without becoming bureaucratic. It's notation-agnostic, meaning teams can draw diagrams using any tool they prefer.
Official WebsiteWhen to use C4 Model
Use the C4 Model when you need to communicate software architecture to different audiences: executives who need the big picture, developers who need technical detail, and new team members who need to understand how systems fit together. It's valuable during system design, architecture reviews, technical due diligence, and documentation efforts.
The model is particularly helpful for distributed systems and microservices, where understanding relationships between components is crucial. It's also useful when onboarding new team members or explaining technical decisions to non-technical stakeholders.
Why choose C4 Model?
Teams choose the C4 Model because it strikes a balance between rigour and practicality. Unlike heavyweight methodologies, it doesn't require expensive tools or extensive training. The four-level hierarchy provides a natural structure for conversations: you can start high-level and drill down as needed. The model's simplicity means diagrams actually get created and maintained, unlike more complex approaches that often get abandoned.