C4 Model Architecture

C4 Diagram Tool

Create C4 model architecture diagrams with AI. Generate Context, Container, and Component views from plain English. Mermaid & PlantUML C4 syntax — version controlled and diff-friendly.

What is the C4 model?

The C4 model is a hierarchical approach to software architecture diagramming created by Simon Brown. Instead of one monolithic architecture diagram, C4 defines four levels of abstraction — Context, Container, Component, and Code — each zooming deeper into the system. This progressive disclosure makes architecture understandable for different audiences.

Think of it like a map: Level 1 (Context) is the satellite view showing your system in the world. Level 2 (Container) zooms to the city level showing major blocks. Level 3 (Component) zooms to the street level showing internal structure. Level 4 (Code) is the building blueprint.

C4 diagrams can be defined as code using Mermaid C4 syntax or PlantUML C4 stdlib. Cybewave Studio generates C4 diagrams from plain English descriptions — describe your system design and get properly structured C4 models instantly.

The four C4 levels

Each level targets a different audience and level of detail.

Level 1

Context Diagram

The big picture. Shows your system as a box surrounded by its users and the external systems it interacts with. Answers: "What does the system do, and who uses it?"

Audience: Everyone — stakeholders, product, engineering, operations

Level 2

Container Diagram

Zoom into the system boundary. Shows the high-level technology choices: web app, API, database, message broker, cache. Answers: "What are the main building blocks?"

Audience: Engineering leadership, architects, senior engineers

Level 3

Component Diagram

Zoom into a single container. Shows the internal components, modules, or services within one deployable unit. Answers: "How is this service structured internally?"

Audience: Engineers working on that specific service or module

Level 4

Code Diagram

Zoom into a single component. Shows classes, interfaces, and their relationships. Typically auto-generated from code rather than hand-drawn.

Audience: Individual developers working within that component

How to create C4 diagrams

AI generates C4 models from system descriptions. No C4 syntax required.

01

Describe your system

Tell the AI about your system, users, and external integrations. It asks follow-up questions about services, data stores, and communication patterns.

02

AI generates C4 diagrams

Get Context, Container, and Component diagrams in Mermaid C4 or PlantUML C4 syntax. Each level zooms deeper into your architecture.

03

Refine with AI assistant

Ask the AI to add services, change relationships, add technology labels, or adjust the level of detail. Iterate until every diagram is accurate.

04

Export and document

Download as PNG/SVG, copy the C4 code to your repo, or generate a full project scaffold with architecture documentation included.

C4 Mermaid code examples

Real C4 syntax generated by Cybewave AI.

E-commerce platform — Context

C4Context
  title E-Commerce System Context
  Person(customer, "Customer", "Browses and buys products")
  System(ecommerce, "E-Commerce Platform", "Handles orders, payments, inventory")
  System_Ext(stripe, "Stripe", "Payment processing")
  System_Ext(email, "Email Service", "Transactional emails")
  Rel(customer, ecommerce, "Uses", "HTTPS")
  Rel(ecommerce, stripe, "Processes payments", "API")
  Rel(ecommerce, email, "Sends emails", "SMTP")

E-commerce platform — Container

C4Container
  title E-Commerce Containers
  Person(customer, "Customer")
  Container(spa, "Web App", "React", "Product browsing and checkout")
  Container(api, "API Server", "Node.js", "REST API for all operations")
  Container(worker, "Order Worker", "Node.js", "Async order processing")
  ContainerDb(db, "PostgreSQL", "SQL", "Orders, products, users")
  ContainerQueue(queue, "RabbitMQ", "AMQP", "Order events")
  Rel(customer, spa, "Uses", "HTTPS")
  Rel(spa, api, "Calls", "JSON/HTTPS")
  Rel(api, db, "Reads/writes", "SQL")
  Rel(api, queue, "Publishes", "AMQP")
  Rel(worker, queue, "Consumes", "AMQP")

Use cases for C4 diagrams

System design documentation

Generate multi-level C4 views of your architecture. Each level targets a different audience — from stakeholders to individual developers.

Architecture Decision Records

Attach C4 diagrams to ADRs showing before/after system state. Track how architecture evolves over time.

Onboarding new engineers

Start with Context (big picture), zoom to Container (services), then Component (internals). Progressive disclosure of complexity.

System design interviews

Practice C4 modeling for interview prep. Describe systems at multiple levels of abstraction — a key skill in senior engineering interviews.

Microservice decomposition

Map monolith components to C4 containers. Plan migration paths with clear before/after architecture views.

Cloud architecture review

Use C4 Container diagrams to show AWS/GCP/Azure services, networking, and data flows at the infrastructure level.

C4 model vs other diagramming approaches

Freeform diagramsNo standard structure, inconsistent across teamFour defined levels with clear purpose and audience
UML onlySingle level of detail, can be overwhelmingProgressive zoom: Context → Container → Component → Code
Whiteboard sketchesLost after the meeting, no versioningDefined as code, versioned in Git, always accessible
Ad-hoc toolingDifferent tools per diagram, no consistencyOne model, multiple views, single source of truth
Documentation-firstDiagrams separate from docs, quickly outdatedC4 code embeds in docs, renders automatically

Frequently asked questions

What is the C4 model?

A hierarchical approach to software architecture diagramming with four levels: Context (system boundary), Container (technology blocks), Component (internal structure), and Code (class-level). Created by Simon Brown.

Do I need to create all four C4 levels?

No. Most teams only need Level 1 (Context) and Level 2 (Container). Add Level 3 (Component) for complex services. Level 4 (Code) is usually auto-generated from source code.

Can Mermaid render C4 diagrams?

Yes. Mermaid has native C4 support with C4Context, C4Container, C4Component, and C4Dynamic diagram types. They render on GitHub and GitLab in Markdown.

How does AI help with C4 modeling?

Describe your system in plain English and Cybewave AI generates properly structured C4 diagrams. It understands system boundaries, containers, and components and applies the right C4 level.

Is the C4 tool free?

Yes. Cybewave offers a free tier with 50 AI credits per month. No credit card required. Paid plans start at $9.89/month.

Create your first C4 diagram

Free to start. 50 AI credits/month. No credit card required.

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