EDGY vs C4 vs Mermaid: Different Tools for Different Questions

I recently added Mermaid support to this site. Rather than writing a tutorial, I thought I’d use the opportunity to compare three concepts that are often mentioned together: EDGY, C4, and Mermaid. The goal isn’t to determine which one is “better.” They solve different problems. This post is therefore both a comparison and a demonstration of how Mermaid diagrams can be embedded directly into Markdown to create living architecture documentation.

Architecture teams often ask: Should we use EDGY? Should we use C4? Is Mermaid replacing both? These questions assume the three approaches solve the same problem. They don’t.

EDGY, C4, and Mermaid operate at different levels of abstraction and complement one another rather than compete. Understanding this distinction helps architects choose the right tool for the right conversation.

EDGY Models the Enterprise

Enterprise architecture begins long before applications and APIs. It starts by understanding the enterprise itself. Questions include:

• What value do we create?
• Which capabilities do we need?
• Who are our stakeholders?
• Which products and services deliver value? EDGY provides a lightweight way to model these relationships without focusing on technology. Enterprise architecture asks questions such as:
• Why does the organization exist?
• How is value created?
• Which capabilities enable the strategy?
• Which products and services deliver that value? Technology supports these conversations, but it should not drive them.

  C4 Models Software Systems

  Once strategy becomes delivery, software architecture requires a different viewpoint. C4 provides a structured way to describe software at multiple levels of abstraction. | Level | Focus | |——–|——-| | Context | How the system fits into its environment | | Container | The major building blocks | | Component | Internal responsibilities | | Code | Implementation details | Rather than creating one large architecture diagram, C4 encourages multiple focused views for different audiences. Each level answers a different question while maintaining a consistent architectural narrative.

  Mermaid Draws the Diagrams

  Unlike EDGY and C4, Mermaid is not a modelling approach. It is a diagramming language. Mermaid allows architecture diagrams to be written as plain text and stored alongside Markdown documentation. This makes diagrams:

• Version controlled
• Easy to review
• Easy to update
• Easy to publish For documentation-as-code, Mermaid has become a natural choice because diagrams evolve alongside the architecture they describe.

  They Solve Different Problems

  Each approach answers a different question. | Tool | Primary Question | |——–|—————–| | EDGY | How is the enterprise designed? | | C4 | How is the software designed? | | Mermaid | How should we communicate it? | Notice that none of these overlap. Using one does not replace the others. Instead, each provides a different viewpoint.

  A Practical Combination

  Many modern architecture repositories benefit from using all three. EDGY provides the enterprise context. C4 describes individual software systems. Mermaid renders both as living documentation. A typical architecture journey might look like this.

  flowchart LR
    Strategy["Enterprise Strategy"]
    EDGY["EDGY"]
    Capability["Capabilities"]
    C4["C4"]
    Mermaid["Mermaid"]
    Documentation["Living Documentation"]
    Strategy --> EDGY
    EDGY --> Capability
    Capability --> C4
    C4 --> Mermaid
    Mermaid --> Documentation
  

  Each layer builds on the previous one while answering a different architectural question. Enterprise Architecture explains why. Software Architecture explains how. Mermaid helps communicate both.

  Choose the Right Viewpoint

  One of the most common mistakes in architecture is trying to use a single notation for every discussion. Capability maps become software diagrams. Context diagrams become enterprise models. Eventually every diagram tries to explain everything—and explains very little. Architecture becomes significantly clearer when each viewpoint has a specific purpose. The goal is not to standardize on one notation. The goal is to communicate the right information to the right audience.

  Final Thoughts

  EDGY is not a replacement for C4. C4 is not a replacement for Mermaid. Mermaid is not a replacement for either. Together they provide a practical path from enterprise strategy to software implementation. The question is therefore not: Which one should we use? The better question is: Which architectural question are we trying to answer? The best architecture repositories don’t standardize on a single diagramming approach. They standardize on answering the right questions with the appropriate viewpoint.