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

# Introduction

> Understand our general API concepts.

## Base URL

Our API is organized around **REST**. It has predictable resource-oriented URLs. We enforce HTTPS in every request
to improve data security, integrity, and privacy. The API does not support HTTP.

All requests contain the following base URL:

```bash theme={null}
https://api.sendforsign.com/api
```

## Authentication

To authenticate you need to add an `X-Sendforsign-Key` header with the contents of the header
being `YOUR_API` where `YOUR_API` is your API key.

```bash theme={null}
X-Sendforsign-Key: YOUR_API_KEY
```

## Response

Sendforsign uses standard HTTP codes to indicate the success or failure of your requests.

In general, `2xx` HTTP codes correspond to success, `4xx` codes are for user-related failures,
and `5xx` codes are for infrastructure issues.

| Property | Description                                  |
| -------- | -------------------------------------------- |
| `200`    | Successful request.                          |
| `400`    | Check that the parameters were correct.      |
| `401`    | The API key used was missing.                |
| `403`    | The API key used was invalid.                |
| `404`    | The resource was not found.                  |
| `429`    | The rate limit was exceeded.                 |
| `5xx`    | Indicates an error with Sendforsign servers. |