What is Container Diagram?
A Container in C4 terms is a runtime-level building block: a web app, an API service, a database, a message broker. The Container diagram shows how these pieces fit together, the protocols between them, and the technology choices. It is the most used C4 level in practice because it maps cleanly to what platform and infrastructure teams deploy.
Related terms
- C4 Model — A lightweight architecture visualization approach that describes software systems across four levels: System Context, Container, Component, and Code.
- System Context Diagram — C4 level 1 diagram showing a software system and its interactions with users and other external systems.
- Component Diagram — C4 level 3 diagram decomposing a container into groups of related functionality (components) and their collaborations.