> ## Documentation Index
> Fetch the complete documentation index at: https://docs.discountdrugnetwork.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Introduction

> This section covers key concepts, authentication strategies, and standard response codes needed to interact with the Discount Drug Network (DDN) API effectively.

## Base URL

The DDN API adheres to REST principles and enforces HTTPS for all requests to ensure data security and integrity. HTTP requests are not supported.

All requests are made to the following base URL:

```
https://api.discountdrugnetwork.com
```

## Response Codes

The DDN API uses standard HTTP codes to indicate request outcomes:

| Status | Description                                                   |
| ------ | ------------------------------------------------------------- |
| 200    | Successful request.                                           |
| 400    | Parameter validation error—check that parameters are correct. |
| 401    | Missing or expired API key.                                   |
| 403    | Invalid or unauthorized API key.                              |
| 404    | Resource not found.                                           |
| 429    | Rate limit exceeded.                                          |
| 5xx    | Server error on DDN's side.                                   |

Refer to the Error Codes section for detailed error explanations and troubleshooting.