Automate Your Docs: Convert JSON to Mermaid JS Flowcharts

JSON to Mermaid JS

There is an old saying in software engineering: “The only up-to-date documentation is the code itself.”

Everything else—the Confluence pages, the PDFs, the whiteboarding photos stored in a forgotten Google Drive folder—is a lie waiting to happen. As soon as you ship a hotfix that changes the checkout flow, that static diagram you drew last week becomes “technical debt.”

For Senior Engineers, this is a massive headache. We want to document our systems so new hires don’t ping us every 5 minutes. But we also hate maintaining documentation because it requires opening a heavy design tool (like Visio or Lucidchart), dragging boxes around, exporting a PNG, and uploading it again.

This friction is why docs die.

The solution is Docs-as-Code. And specifically, using tools to convert JSON to Mermaid JS allows us to treat diagrams just like we treat our source code: version-controlled, diffable, and automated.

The “Docs-as-Code” Philosophy

If you aren’t familiar with Mermaid.js, it is a JavaScript-based diagramming and charting tool that renders Markdown-inspired text definitions to create diagrams dynamically.

Instead of drawing a box, you write:

graph TD;
    A[API Request] --> B{Valid?};
    B -- Yes --> C[Process Data];
    B -- No --> D[Return 400];

GitHub, GitLab, and Notion all render this natively. This is great, but writing Mermaid syntax manually for a massive state machine or a complex config file is tedious. You are essentially writing code to draw pictures of code.

This is where automation comes in. Your application already emits the truth about its structure in JSON format—whether that’s a Redux state tree, a Swagger/OpenAPI spec, or a custom configuration object.

By using a generator to convert JSON to Mermaid JS, you close the loop. You stop drawing and start generating.

Use Case: Visualizing Microservices Config

Let’s talk about a real scenario. You are running a microservices architecture orchestrated by a massive JSON configuration file. This file dictates which services talk to which topics on Kafka, which databases they access, and their failover policies.

A new developer joins the team. They ask, “How does the Order Service interact with the Inventory Service?”

You could walk them through the 4,000-line JSON config. Or, you could copy that JSON, paste it into a generator, and instantly produce a Flowchart or Sequence Diagram.

Better yet, you can add this to your build pipeline.

The “Living ReadMe” Strategy

Here is a workflow I have implemented in previous teams to kill “doc rot” forever:

1. The Source: We have a services.json file that defines our architecture.
2. The Tool: We use a JSON-to-Mermaid generator to parse this file.
3. The Output: The tool gives us the raw Mermaid syntax.
4. The Commit: We paste this syntax into our README.md inside a mermaid code block.

Now, whenever a developer opens the repo on GitHub, they see a perfectly accurate, up-to-the-minute diagram of the system. If the JSON config changes, the diagram updates automatically (if you script the generation) or takes 10 seconds to update manually.

Why Mermaid? Why Not a JPEG?

You might ask, “Why go through the trouble of generating code? Why not just generate an image?”

1. Diffability: If you change a JPEG, Git just shows “Binary file changed.” If you change Mermaid text, Git shows you exactly what changed: CustomerNode --> OrderNode became CustomerNode --> IntermediateNode --> OrderNode. You can review architectural changes in a Pull Request.
2. Searchability: You can grep (search) through Mermaid text. You can’t search inside a PNG.
3. Dark Mode Support: Mermaid diagrams on GitHub adapt to the user’s theme. A white-background JPEG looks blindingly bright to a developer using Dark Mode at 2 AM.

From JSON State to Sequence Diagrams

Another powerful application is debugging asynchronous flows.

Imagine you are debugging a race condition in your frontend. You have a log of actions that occurred: INIT, FETCH_START, FETCH_SUCCESS, UPDATE_UI.

This log is essentially a JSON array of objects.

Reading the timestamps is one thing. But if you paste that JSON array into a generator and select Sequence Diagram, you can visualize the timeline. You might see that UPDATE_UI triggered before FETCH_SUCCESS returned.

The visual gap on the timeline makes the race condition obvious in a way that timestamps don’t.

Conclusion

We need to stop treating documentation as an “art project” separate from our engineering work. Documentation is engineering.

By using tools that convert JSON to Mermaid JS, you are bridging the gap between data and understanding. You are enabling a workflow where diagrams are cheap, disposable, and always accurate.

Stop drawing boxes. Start generating them.

FAQ JSON to Mermaid JS

1. What does “JSON to Mermaid JS” mean?

It refers to converting JSON data into Mermaid JS diagram syntax. Mermaid JS is a text-based diagramming language used to create flowcharts, ER diagrams, class diagrams, sequence diagrams, and more. Converting JSON automates diagram creation without writing Mermaid syntax manually.

2. Why convert JSON into Mermaid JS diagrams?

Because JSON can be hard to visualize when it’s deeply nested. Converting it into Mermaid diagrams helps developers quickly understand structure, relationships, data flow, and logic. It’s ideal for documentation, onboarding, architecture reviews, and API visualization.

3. What types of Mermaid diagrams can JSON be converted into?

Depending on the conversion logic or tool, JSON can generate:

• Flowcharts
• ER diagrams
• Class diagrams
• State diagrams
• Sequence diagrams
• Mindmaps
  This makes Mermaid JS extremely flexible for representing structured JSON data.

4. Can I convert any JSON file to Mermaid JS syntax?

Yes, as long as the JSON is valid. However, very complex or irregular JSON structures may produce large diagrams that need simplifying or manual editing.

5. Do I need a JSON Schema to generate Mermaid JS?

Not necessarily. Many tools parse raw JSON and infer relationships automatically. But JSON Schema can help produce more accurate class or ER diagrams.

6. Can JSON from API responses be converted into Mermaid diagrams?

Absolutely. API responses (especially nested objects) are great candidates for ER or class diagrams to quickly visualize structure and relationships.

7. What tools can generate Mermaid JS from JSON?

You can use:

• Online JSON-to-Mermaid generators
• JSON Schema to Mermaid tools
• Custom scripts (JavaScript/Python) that output Mermaid syntax
• VS Code extensions that support Mermaid + JSON conversions

8. Can I edit the Mermaid JS diagram after converting from JSON?

Yes. Mermaid syntax is plain text, so you can modify nodes, relationships, labels, colors, and layout manually after generating the initial version.

9. Is Mermaid JS good for documentation?

Yes — Mermaid is widely used in README files, wikis, and documentation platforms like GitHub, GitLab, Notion, and MkDocs. It allows diagrams to be maintained as code, ensuring easier version control.

10. Can Mermaid JS output be exported as images or PDFs?

Yes. Most Mermaid renderers and editors allow exporting diagrams as PNG, SVG, or PDF for presentation, documentation, or architecture planning.