> ## Documentation Index
> Fetch the complete documentation index at: https://next-developers.opencard.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Overview

> OpenCard integration paths for card issuers — deliver transactions to connected EMS apps, or fetch digital receipts from the merchant network.

This section is for **card issuers** — banks and card programs integrating with OpenCard.

***

## Two integrations — pick what you need

OpenCard offers **two separate APIs**. Most issuers start with transaction delivery; digital receipts is optional and runs on a different host.

<CardGroup cols={2}>
  <Card title="Issuer Integration" icon="credit-card" href="/card-issuers/issuer-integration">
    Receive signed TPAs, register cards, and push transaction states (`authorized`, `cleared`, `invoiced`, `deleted`) to OpenCard for connected Expense Management Systems.
  </Card>

  <Card title="Digital receipts" icon="receipt" href="/card-issuers/digital-receipts">
    Submit transactions to `receipts.opencard.io` for merchant receipt matching — independent from transaction delivery.
  </Card>
</CardGroup>

***

## Issuer Integration at a glance

|                           |                                                                              |
| ------------------------- | ---------------------------------------------------------------------------- |
| **Base URL (sandbox)**    | `https://sandbox-api.opencard.io`                                            |
| **Base URL (production)** | `https://api.opencard.io`                                                    |
| **API prefix**            | `/api/v1/issuers/{slug}/`                                                    |
| **Auth**                  | OAuth 2.0 client credentials                                                 |
| **Credentials**           | `client_id`, `client_secret`, and `{slug}` delivered when integration starts |

→ [How it works](/card-issuers/issuer-integration)