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Architecture

C4 container diagram template

People, web and mobile apps, API, database and external systems

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Preview of the C4 container diagram template

What’s inside

Nodes
10
Packs
C4 Model
Category
Architecture

Works on the Free plan: 15 diagram nodes + 150 notes, text, stickers & mind map topics per diagram.

The C4 model describes software at four levels: context, containers, components and code. This template is level 2, the container diagram: a customer uses a web application and a mobile app, both call an API application, and the API reads and writes an orders database and publishes events to a message broker.

An order worker consumes those events and sends confirmations through an external email service, while the API charges cards through an external payment provider. Each container shows its technology and one sentence about its job, relationships say what happens and over which protocol, and the system boundary separates what you build from what you use.

When to use it

  • Explaining the moving parts of a system to new developers, product managers or security reviewers.
  • Deciding where a new feature belongs before you split or merge services.
  • Documenting an architecture decision with a picture that matches the code structure.
  • Preparing the container view that sits between a context diagram and component diagrams.

How to use it

  1. Rename the system boundary and the containers, and write one sentence about what each container is responsible for.

  2. Set the technology on each container and the protocol on each relationship, such as JSON over HTTPS or SQL.

  3. Add the people and external systems your users and integrations depend on, and remove what you do not have.

  4. Share a link with the team or export the diagram for the architecture document, and save a revision when the containers change.

Questions

What is a container in the C4 model?

A container is something that runs code or stores data on its own: a web application, a mobile app, an API, a database, a message broker or a background worker. It is not the same as a Docker container, although a C4 container is often deployed as one.

Can I draw the other C4 levels too?

Yes. The C4 pack has people, software systems, containers, components, databases, system and container boundaries and deployment nodes, so you can draw context, container, component and deployment diagrams on the same canvas.

Can I generate a C4 diagram from text?

Not from Structurizr DSL or Mermaid C4 syntax. Start from this template, or connect your AI agent to Archboard over MCP and describe the containers; the agent draws them on your canvas and you edit the result.

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Related use case

C4 architecture diagrams

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