Diagramming as Code with Mermaid: A Better Way to Track System Design

In software engineering, keeping architecture diagrams up to date is often challenging. They’re scattered across slides, notebooks, or buried in documentation that no one remembers to update. Enter Mermaid, a tool that brings diagramming into your codebase, ensuring your system design stays current and accessible.

Mermaid enables Diagramming as Code, a concept that treats diagrams as part of your version-controlled codebase. This approach eliminates the disconnect between diagrams and implementation, making it easier to visualize workflows, processes, and architectures alongside your source code.

Why Choose Mermaid?

Mermaid is lightweight, accessible, and requires no complex installations. It’s perfect for creating flowcharts, sequence diagrams, class diagrams, and even C4 diagrams, all with simple syntax. Plus, because it integrates seamlessly with tools like VSCode, GitHub, and GitLab, it fits naturally into your development workflow.

By storing diagrams in code, you can track changes alongside commits, ensuring architecture evolves in sync with the project. For instance, if your team adds a new service, you can update and version your architecture diagram directly in the same pull request.

Quickly Generate Diagrams with the Mermaid Live Editor

If you need to create a diagram quickly without setting up anything locally, you can use the Mermaid Live Editor. This browser-based tool allows you to write Mermaid code and instantly preview the diagram.

🚀 Cool Feature: The Mermaid Live Editor stores the diagram directly in the URL, so you can easily save it and share it with your team for review. This makes it a great tool for collaborative architecture discussions or quick documentation updates.

Getting Started with Mermaid

Mermaid allows you to create different types of diagrams, making it a great tool for web development architecture, API interactions, and software component relationships. Below are some common diagram types and their real-world web development use cases.

1. Flowchart (Frontend to Backend Request Flow)

Use case: Illustrate how a React frontend interacts with a Node.js API and a PostgreSQL database.

graph TD
    A[User] -->|Clicks Button| B[React Frontend]
    B -->|Sends API Request| C[Node.js Backend]
    C -->|Fetches Data| D[PostgreSQL Database]
    D -->|Returns Data| C
    C -->|Sends Response| B
    B -->|Updates UI| A

2. Sequence Diagram (User Authentication Flow)

Use case: Represent how a user logs in using an OAuth-based authentication flow.

sequenceDiagram
    participant User
    participant Frontend
    participant Backend
    participant OAuth Server

    User->>Frontend: Enter Credentials
    Frontend->>Backend: Sends Login Request
    Backend->>OAuth Server: Requests Token
    OAuth Server-->>Backend: Returns Token
    Backend-->>Frontend: Sends JWT Token
    Frontend-->>User: Login Successful

3. Class Diagram (Models in a Web App)

Use case: Define object relationships in a Django or Rails application.

classDiagram
    class User {
        +id: Int
        +username: String
        +email: String
    }
    class Post {
        +id: Int
        +title: String
        +content: Text
        +user_id: Int
    }
    User "1" --> "Many" Post : owns

4. C4 Diagram (System Architecture)

Use case: Visualize a microservices-based web architecture, including frontend, API gateway, and database services.

C4Context
  title System Architecture Overview

  Person(user, "User", "A person interacting with the system")
  
  System_Boundary(webApp, "Web Application") {
    System(frontend, "Frontend App", "Next.js (Vercel)")
    System(backend, "Backend API", "Node.js (AWS Lambda)")
    SystemDb(database, "Database", "PostgreSQL (AWS RDS)")
  }
  
  Rel(user, frontend, "Uses", "HTTPS")
  Rel(frontend, backend, "Requests Data", "REST API")
  Rel(backend, database, "Reads/Writes Data", "PostgreSQL")

Integrating Mermaid into Your Development Workflow

To make Mermaid diagrams more effective:
✅ Store diagrams in Git repositories to track changes.
✅ Embed diagrams in README files or Docusaurus for documentation.
✅ Automate updates in CI/CD pipelines to maintain consistency.
✅ Use Confluence, Notion, or Obsidian to share diagrams with the team.

Final Thoughts

Mermaid is a game-changer for software engineers aiming to reduce the gap between design and implementation. By treating diagrams as part of your codebase, you’ll not only improve documentation but also enhance collaboration across your team.

• Want to quickly create a diagram? Try the Mermaid Live Editor and share your diagrams instantly!
• Ready to integrate Mermaid into your project? Check out the Getting Started Guide to set up Mermaid in your workflow.
• Need integrations? See the full list of supported tools in the Mermaid Integrations Page to explore compatibility with platforms like GitHub, GitLab, Notion, and more.