> For the complete documentation index, see [llms.txt](https://docs.finpay.id/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.finpay.id/finpay-pg/core-api.md).

# Core API

### Introduction <a href="#introduction" id="introduction"></a>

**Core API** enables communication between your system and Finpay payment gateway system. The payment page and data input is native to the merchant's website/application, without having redirect to a Finpay PG Hosted page. Having the payment form on the merchant page does not compromise the security of the cardholder however, none of the cardholder data will actually be stored on the merchant’s server.

### Transaction Flow <a href="#transaction-flow" id="transaction-flow"></a>

The overall end-to-end payment process in Core API is illustrated in following sequence diagram:

```mermaid
sequenceDiagram
    actor Customer as End Customer
    participant Merchant
    participant Finpay
    participant sof as Payment Channel Provider

    Customer->>Merchant: Choose payment method
    Merchant->>Finpay: Request Payment initiate
    Finpay->>Merchant: Response Payment initiate
    Merchant->>Customer: Show payment details
    Customer-->>Customer: Pay on selected provider
    sof->>Finpay: Callback Notification
    Finpay->>Merchant: Callback Notification
    Merchant->>Customer: Notify transaction status
```


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