# Getting Started

The **Pay.io Payment Gateway API** enables merchants to build a full cashier solution directly into your websites or applications. With a single integration, you can:

* Trigger **deposits** and **withdrawals**
* Show **real-time balances** and transaction history
* Access multiple crypto payment providers through **native MESH integration**

While business owners manage their accounts and configurations in the **Merchant Console**, the **Payment Gateway API** is what powers the end-user cashier experience.

***

### Prerequisites

Before you start making API calls, you'll need to:

* **Onboard as a merchant with Pay.io** -  our team will configure your account, including enabling key currencies, according to your needs.
* **Obtain your API key** - Found in the Merchant Console or provided by our support team.
* **Generate RSA key pair -** You’ll provide Pay.io your public key during setup (see [Authorisation](/api-reference/core-concepts/authorisation.md) for details).
* **Set up request signing** — Each API call requires a nonce and RSA-SHA256 signature.

***

### Pay.io APIs Overview

#### Merchant API

Used by your backend to configure cashier options:

* [**Currencies API** ](/api-reference/merchant-console-api/get-a-list-of-available-currencies.md#get-a-list-of-available-currencies)- Used to retrieve the list of enabled currencies for you.
* [**Transactions API**](/api-reference/merchant-console-api/get-a-list-of-merchant-transactions.md) - Access transaction history across users and retry payouts requiring approval.

#### User Payment API

Used to serve your end-users inside the cashier through our payment gateway experience:

* [**Deposits API** ](/api-reference/user-payment-api/create-a-deposit-address.md)- Generate unique deposit addresses or create wallet deposit links.
* [**Withdrawals API** ](/api-reference/user-payment-api/create-a-user-withdrawal.md)- Allow users to request withdrawals to personal wallets.
* [**User Transactions API** ](/api-reference/user-payment-api/get-a-list-of-user-transactions.md)- Display a user’s transaction history in your cashier UI.

***

### Making Your First API Call: List Currencies

Once your merchant account is onboarded, your **first step** is to list which currencies are available for your cashier to set up the Payment Gateway. 

#### Request

```bash
curl --location 'https://gateway.stage.pay.io/v1/merchant/currencies' \
--header 'X-API-Key: YOUR_API_KEY' \
--header 'X-API-Nonce: YOUR_UUID_NONCE' \
--header 'X-API-Signature: SIGNATURE'
```

#### Response (example)

```json
{
  "currencies": [
    {
      "id": "1270e0a2-593b-5272-8c0e-90ba5552d921",
      "name": "SOL",
      "currency_code": "SOL",
      "symbol": "◎",
      "network": "Solana",
      "currency_icon": "https://cdn.hub88.io/hub-wallet/SOL-ic.svg"
    },
    {
      "id": "990cd2f7-b169-5665-b0e1-05cc46ae4209",
      "name": "USDC",
      "currency_code": "USDC",
      "symbol": "$",
      "network": "Base Chain"
    }
  ]
}
```

***

### Next Steps For Payment Gateway

Once you have your supported currencies, you can:

* Request a **deposit address** for a user ([`POST /v1/user/deposit/address`](/api-reference/user-payment-api/create-a-deposit-address.md))
* Initiate a **withdrawal** ([`POST /v1/user/withdraw`](/api-reference/user-payment-api/create-a-user-withdrawal.md))
* Fetch **transactions** for a user ([`POST /v1/user/transactions`](/api-reference/user-payment-api/get-a-list-of-user-transactions.md)) or across your merchant ([`POST /v1/merchant/transactions`](/api-reference/merchant-console-api/get-a-list-of-merchant-transactions.md))

See the [Authorisation](/api-reference/core-concepts/authorisation.md) for details on how to sign and authenticate your requests.


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