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

# Subtotal API

> Build applications that integrate with Subtotal

## Overview

The Subtotal API lets brands and developers build experiences around customer-permissioned retail purchases.

The Subtotal API follows REST principles and uses standard HTTP methods and JSON payloads, making it straightforward to work with in any modern programming language or framework.

## Base URL

Append an endpoint to the base URL root address to form a complete request URL.

```
https://api.subtotal.com
```

## Authentication

All requests must include an API key for authentication.

Include the following header in each request:

```json theme={null}
headers = {
  "X-Api-Key": "{yourkeyvalue}"
}
```

## Authorization

We reserve the *Authorization* header for endpoints that require a [connection token](/docs/api-reference/connections/create-connection-token).

```json theme={null}
headers = {
  "Authorization": "Bearer: {connection_token}"
}
```