---
title: Quickstart
description: Accept your first test crypto payment with Coinetic in 15 minutes: get sandbox API keys, create an invoice, redirect to checkout and handle the webhook.
url: https://coinetic.money/docs/quickstart/
lang: en
---

# Quickstart

Your first sandbox payment in 15 minutes. You'll need a Node.js, PHP, Python or Go server; there are examples for all four.

> **What you'll have at the end.** Your site creates an invoice, the customer pays on the Coinetic page (in the sandbox, with a button), and your server receives a webhook and fulfills the order exactly once.

## 1. Get sandbox keys

- Sign up in the [sandbox dashboard](https://sandbox.coinetic.money/merchant) and enable 2FA.
- “Keys & webhooks” → “Create key”: save the `key_id` (`ak_…`) and the secret.
- “Keys & webhooks” → “Add endpoint”: enter your handler URL, such as `https://shop.example/webhooks/coinetic` (in the sandbox, `http://localhost:3000/…` works too). Save the webhook secret.

Secrets are shown **only once**. Put them in your server's environment variables:

`.env (never commit!)`

```bash
API_KEY=ak_...
API_SECRET=...
WEBHOOK_SECRET=...
```

## 2. Download a client

Each client is a single file with no external dependencies: request signing, creating and fetching invoices, webhook verification. [Download one for your language →](https://coinetic.money/docs/sdks/)

## 3. Create an invoice

Pass the price as a string, in USD, EUR, USDT or USDC. Derive the `Idempotency-Key` from the order number so a retry after a timeout returns the same invoice.

**Node.js** — `create-invoice.js`

```js
import { CoineticClient } from "./cryptopay.js";

const cp = new CoineticClient({ baseUrl: "https://sandbox.coinetic.money", keyId: process.env.API_KEY, secret: process.env.API_SECRET });

const invoice = await cp.createInvoice({
  order_id: "ORDER-1001",                 // your order number, unique per merchant
  price_amount: "25.00",                  // a string, not a number
  price_currency: "USD",
  return_url: "https://shop.example/orders/ORDER-1001",
  metadata: { user_id: "42" },
}, "order-ORDER-1001");                   // Idempotency-Key

console.log(invoice.checkout_url);        // https://sandbox.coinetic.money/pay/inv_…#t=…
```

**PHP** — `create-invoice.php`

```php
require 'Cryptopay.php';

$cp = new \Cryptopay\Client('https://sandbox.coinetic.money', getenv('API_KEY'), getenv('API_SECRET'));

$invoice = $cp->createInvoice([
    'order_id'       => 'ORDER-1001',
    'price_amount'   => '25.00',
    'price_currency' => 'USD',
    'return_url'     => 'https://shop.example/orders/ORDER-1001',
    'metadata'       => ['user_id' => '42'],
], 'order-ORDER-1001');

echo $invoice['checkout_url'];
```

**Python** — `create_invoice.py`

```py
import os
from cryptopay import CoineticClient

cp = CoineticClient("https://sandbox.coinetic.money", os.environ["API_KEY"], os.environ["API_SECRET"])

invoice = cp.create_invoice({
    "order_id": "ORDER-1001",
    "price_amount": "25.00",
    "price_currency": "USD",
    "return_url": "https://shop.example/orders/ORDER-1001",
    "metadata": {"user_id": "42"},
}, "order-ORDER-1001")

print(invoice["checkout_url"])
```

**Go** — `main.go`

```go
cp := &cryptopayclient.Client{
	BaseURL: "https://sandbox.coinetic.money",
	KeyID:   os.Getenv("API_KEY"),
	Secret:  os.Getenv("API_SECRET"),
	HTTP:    &http.Client{Timeout: 10 * time.Second},
}
inv, err := cp.CreateInvoice(ctx, cryptopayclient.CreateInvoice{
	OrderID:       "ORDER-1001",
	PriceAmount:   "25.00",
	PriceCurrency: "USD",
	ReturnURL:     "https://shop.example/orders/ORDER-1001",
	Metadata:      map[string]string{"user_id": "42"},
}, "order-ORDER-1001")
if err != nil {
	return err
}
fmt.Println(inv.CheckoutURL)
```

## 4. Send the customer to checkout

Redirect the browser to `invoice.checkout_url` (HTTP 303). The customer picks a currency and sees the address, amount and QR code. In the sandbox, test payment buttons appear below the payment details: “Pay exact,” “Underpay 10%,” “Overpay 10%,” “Half amount” and “Pay remainder.”

> **Don't embed it in an iframe.** The checkout page blocks embedding to protect against address spoofing. Open it in the same tab or in the app's system browser.

## 5. Receive the webhook

The order is always the same: **verify the signature → drop duplicates → re-check the status via the API → fulfill the order once → respond with 2xx**.

**Node.js** — `webhook.js`

```js
import express from "express";
import { verifyWebhook } from "./cryptopay.js";
// cp is the client from step 3. alreadyProcessed / markProcessed / fulfil are your own functions.

const app = express();

// express.raw: the signature is computed over the raw bytes, so don't use express.json() on this route
app.post("/webhooks/coinetic", express.raw({ type: "application/json" }), async (req, res) => {
  let event;
  try {
    event = verifyWebhook(process.env.WEBHOOK_SECRET, req.headers, req.body);
  } catch (e) {
    return res.status(e.status ?? 400).end();               // 401: invalid signature, 400: stale timestamp
  }
  try {
    const eventId = req.headers["x-webhook-id"];
    if (await alreadyProcessed(eventId)) return res.sendStatus(200);
    const inv = await cp.getInvoice(event.data.invoice_id); // status comes from the API, not the webhook
    if (inv.status === "paid" || inv.status === "overpaid") await fulfil(inv.order_id);
    await markProcessed(eventId);
    res.sendStatus(200);
  } catch (e) {
    console.error(e);
    res.sendStatus(500);                                    // non-2xx: Coinetic will retry delivery
  }
});

app.listen(3000);
```

**PHP** — `webhook.php`

```php
require 'Cryptopay.php';

$headers = array_change_key_case(getallheaders(), CASE_LOWER);
$raw = file_get_contents('php://input');                   // raw body, before json_decode
try {
    $event = \Cryptopay\verify_webhook(getenv('WEBHOOK_SECRET'), $headers, $raw);
} catch (\Cryptopay\CryptopayException $e) {
    http_response_code($e->status);
    exit;
}
if (already_processed($headers['x-webhook-id'])) { http_response_code(200); exit; }

$inv = $cp->getInvoice($event['data']['invoice_id']);       // status comes from the API
if (in_array($inv['status'], \Cryptopay\PAID_STATUSES, true)) {
    fulfil($inv['order_id']);
}
mark_processed($headers['x-webhook-id']);
http_response_code(200);
```

**Python** — `webhook.py`

```py
import os
from flask import Flask, request
from cryptopay import verify_webhook, CryptopayError, PAID_STATUSES

app = Flask(__name__)

@app.post("/webhooks/coinetic")
def webhook():
    headers = {k.lower(): v for k, v in request.headers.items()}
    try:
        event = verify_webhook(os.environ["WEBHOOK_SECRET"], headers, request.get_data())
    except CryptopayError as e:
        return "", e.status
    if already_processed(headers["x-webhook-id"]):
        return "", 200
    inv = cp.get_invoice(event["data"]["invoice_id"])      # status comes from the API
    if inv["status"] in PAID_STATUSES:
        fulfil(inv["order_id"])
    mark_processed(headers["x-webhook-id"])
    return "", 200
```

**Go** — `webhook.go`

```go
func webhook(w http.ResponseWriter, r *http.Request) {
	raw, err := io.ReadAll(http.MaxBytesReader(w, r.Body, 1<<20))
	if err != nil {
		w.WriteHeader(http.StatusBadRequest)
		return
	}
	if err := cryptopayclient.VerifyWebhook(os.Getenv("WEBHOOK_SECRET"), r.Header, raw, time.Now(), 5*time.Minute); err != nil {
		w.WriteHeader(http.StatusUnauthorized)
		return
	}
	var ev struct {
		Data struct{ InvoiceID string `json:"invoice_id"` } `json:"data"`
	}
	if err := json.Unmarshal(raw, &ev); err != nil {
		w.WriteHeader(http.StatusBadRequest)
		return
	}
	inv, err := cp.GetInvoice(r.Context(), ev.Data.InvoiceID) // status comes from the API
	if err != nil {
		w.WriteHeader(http.StatusInternalServerError) // Coinetic will retry
		return
	}
	if cryptopayclient.PaidStatuses[inv.Status] {
		fulfilOnce(inv.OrderID)
	}
	w.WriteHeader(http.StatusOK)
}
```

## 6. Bring the customer back

After payment, the page shows a “Return to store” button that takes the customer to your `return_url`. Show the order status there **from your own database**. If the webhook hasn't arrived yet, re-check with `GET /v1/invoices/{id}`.

## Next steps

- [Run every scenario in the sandbox](https://coinetic.money/docs/sandbox/): underpayment, overpayment, expired invoice.
- [Handle the remaining events](https://coinetic.money/docs/webhooks/): `underpaid`, `expired`, `reorged`.
- [Work through the go-live checklist](https://coinetic.money/docs/go-live/) before taking real money.