# API Reference (https://docs.billwave.example/api-reference)

API Reference [#api-reference]

Base URL: `https://api.billwave.example` (production) · `https://sandbox.billwave.example` (sandbox)

The **Server URL** selector in the playground can use either environment. Switch it to `https://sandbox.billwave.example` when you want to test against sandbox data and test provider keys.

All endpoints require authentication via API key in the `Authorization` header:

```bash
Authorization: Bearer billwave_sk_your_api_key
```

Browse the endpoints in the sidebar to see interactive documentation with request/response schemas, code samples, and a built-in playground.