C4 model
A common visual language for explaining how a system actually fits together
What it is
About C4 model
Created by Simon Brown, the C4 model gives architects and engineers a consistent way to zoom from a system's high-level context down to individual components without the ambiguity of free-form boxes-and-arrows diagrams. It's not a piece of software itself but a modelling approach, typically implemented using tools like Structurizr, PlantUML, Mermaid or diagrams.net.
What you can do with it
Capabilities
Communicate system architecture clearly to both technical and non-technical audiences
Document context, container, component and code-level views consistently
Onboard new engineers faster with a standard architectural map
Support architecture decision records (ADRs) with clear diagrams
Diagram microservice boundaries and integration points
How to learn it
Learning Resources
c4model.com — Simon Brown's official site with guides and examples
Simon Brown's book 'Software Architecture for Developers'
Structurizr's free tutorials and example workspace
Practise by diagramming an existing system you already know well
Pro Tip
Don't try to model everything at once — start with just the System Context diagram; it forces you to clarify scope and boundaries before drilling into components.
Skills that use this tool
Roles that use this tool