export const metadata = {
  title: `${pageNumber} Your First Customizations`,
}

# {metadata.title}

In this chapter, you’ll build your first customizations with Medusa.

You'll create a `GET` API route at the path `/hello-world`. An API route exposes your application's commerce features to frontend clients, such as the admin dashboard or a storefront.

Medusa has [Store](!api!/store) and [Admin](!api!/admin) API routes, and you can create custom API routes for your custom features.

## 1. Create API Route

API Routes expose business logic through REST APIs. You can create custom API routes to expose custom business logic.

To create an API route, create the file `src/api/hello-world/route.ts` with the following content:

```ts title="src/api/hello-world/route.ts"
import type {
  MedusaRequest,
  MedusaResponse,
} from "@medusajs/framework/http"

export const GET = (
  req: MedusaRequest,
  res: MedusaResponse
) => {
  res.json({
    message: "Hello, world!",
  })
}
```

---

## 2. Test Customizations

To test out your customizations:

1. Start the Medusa application:

```bash npm2yarn
npm run dev
```

2. Send a `GET` request to `/hello-world`:

```bash
curl http://localhost:9000/hello-world
```

In the response, you’ll receive the following object:

```json
{
  "message": "Hello, world!"
}
```

---

## Next Steps

Congratulations, you’ve made your first customization with Medusa!

You can now start your in-depth learning journey to become an expert.