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

# Introduction

The Bringin REST API lets you onboard users, create crypto ↔ fiat connections, top up debit cards, and check balances and transactions.

## Base URLs

| Environment | URL                       |
| ----------- | ------------------------- |
| Sandbox     | `https://dev.bringin.xyz` |
| Production  | `https://api.bringin.xyz` |

## Authentication

All requests require an `api-key` header:

```bash theme={null}
api-key: YOUR_API_KEY
```

* **Master key** — for onboarding endpoints
* **Per-user key** — for everything else

Some endpoints also require [HMAC signing](/authentication/hmac-signing).

See [Authentication](/authentication/overview) for details.