Developers

One API. Every USDT network.

A 100% NTPAY-compatible REST API: two endpoints, signed callbacks and a hosted checkout. Already on NTPAY? Change the base URL and you're done.

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Getting started

Overview

Cradex is a non-custodial USDT gateway. You create an invoice from your server, redirect the customer to the hosted checkout, and the payment goes straight to your own wallet. We watch the chain, then notify your callback_url.

1. Create

Call AddInvoice with the amount and your order ID.

2. Redirect

Send the customer to url_payment to pay on any network.

3. Confirm

Receive a signed callback or poll GetInvoiceStatus.

Base URL	https://cradex.net/api
Methods	GET and POST (query string, form-encoded or JSON)
Response	JSON, always HTTP 200 — check the status field
Encoding	UTF-8
CORS	Allowed — but never call the API from a browser (it exposes your api_key)

Security

Authentication

Every request carries two parameters: merchant_id and api_key. Create a merchant in your Business dashboard, add at least one receiving wallet and copy the credentials from the API credentials tab.

The merchant must be Active.
It must have at least one enabled receiving wallet.
Your account needs a positive USD balance to cover gateway fees.

Keep your API key on the server. Never embed it in a website, mobile app or public repository. You can rotate it at any time from the dashboard.

Endpoint

Create invoice

Creates a new USDT invoice and returns the hosted checkout link to redirect the customer to.

POSTGEThttps://cradex.net/api/AddInvoice

Parameter	Type	Required	Description
merchant_id	string	Required	Your merchant ID (max 50 chars).
api_key	string	Required	Secret API key of the merchant (max 255 chars).
name	string	Required	Invoice title shown at checkout, e.g. “Order #4821” (max 255).
description	string	Required	Invoice details (max 500).
amount	float	Required	Amount in USDT. Minimum 1.
request_id	string	Optional	Your own unique order ID, echoed back in responses and callbacks (max 100).
callback_url	url	Optional	Where Cradex sends status callbacks.
success_url	url	Optional	Where the customer returns after a successful payment.
cancel_url	url	Optional	Where the customer returns if the invoice expires or is cancelled.

curl -X POST https://cradex.net/api/AddInvoice \
  -d merchant_id=YOUR_MERCHANT_ID \
  -d api_key=YOUR_API_KEY \
  -d name="Order #4821" \
  -d description="Premium plan – 12 months" \
  -d amount=249 \
  -d request_id=ORDER_4821 \
  -d callback_url=https://shop.example.com/webhooks/cradex \
  -d success_url=https://shop.example.com/thank-you \
  -d cancel_url=https://shop.example.com/cart

Response

200 OK

{
  "status": "success",
  "msg": "Invoice creation successful!",
  "data": {
    "trans_id": "TX2604571052543841",
    "request_id": "ORDER_4821",
    "amount": "249.013",
    "status": "waiting",
    "url_payment": "https://cradex.net/payment/TX2604571052543841"
  }
}

data.amount may differ slightly from the requested amount: Cradex adds a small unique decimal (e.g. 249 → 249.013) so each payment can be matched on-chain. The customer must send this exact amount.

Endpoint

Get invoice status

Returns the current state of an invoice. Use it to double-check a callback or to poll when callbacks are not an option.

POSTGEThttps://cradex.net/api/GetInvoiceStatus

Parameter	Type	Required	Description
merchant_id	string	Required	Your merchant ID.
api_key	string	Required	Secret API key of the merchant.
trans_id	string	Required	Transaction ID returned by AddInvoice.

curl "https://cradex.net/api/GetInvoiceStatus?merchant_id=YOUR_MERCHANT_ID&api_key=YOUR_API_KEY&trans_id=TX2604571052543841"

Response

200 OK

{
  "status": "success",
  "msg": "Get invoice status successful!",
  "data": {
    "trans_id": "TX2604571052543841",
    "request_id": "ORDER_4821",
    "amount": "249",
    "received": "249.013",
    "status": "completed",
    "from_address": "TXyz123abc456def789ghi",
    "transaction_id": "abc123def456…0123456789ab",
    "create_gettime": "2026-10-31 10:30:00",
    "update_gettime": "2026-10-31 10:41:22"
  }
}

Webhooks

Callbacks

When an invoice becomes completed or expired, Cradex calls your callback_url with these 9 fields — exactly like NTPAY. Fields are sent as a GET query string; if your URL contains type=HostBill they are sent as a POST form instead.

Field	Description
request_id	Your order ID from AddInvoice.
trans_id	Cradex transaction ID.
merchant_id	Your merchant ID.
api_key	Your merchant API key (for NTPAY compatibility).
amount	Original requested amount.
received	Amount actually received (0 when expired).
status	completed or expired.
from_address	Sender wallet address (empty when expired).
transaction_id	On-chain transaction hash (empty when expired).

Example callback

GET https://shop.example.com/webhooks/cradex
    ?request_id=ORDER_4821
    &trans_id=TX2604571052543841
    &merchant_id=YOUR_MERCHANT_ID
    &api_key=YOUR_API_KEY
    &amount=249
    &received=249.013
    &status=completed
    &from_address=TXyz123abc456def789ghi
    &transaction_id=abc123def456…0123456789ab

X-Cradex-Timestamp: 1793442082
X-Cradex-Signature: sha256=5f0c1a…e9b2

Delivery & retries

Only an HTTP 2xx response counts as delivered. Anything else (or a timeout) is retried on this schedule, up to 8 attempts in total:

#1 Immediately#2 1 min#3 5 min#4 15 min#5 1 h#6 3 h#7 6 h#8 12 h

Every attempt is logged on the invoice page in your dashboard, where you can also resend a callback manually. Make your handler idempotent — the same invoice may be delivered more than once.

Webhooks

Verifying signatures

On top of the NTPAY fields, each callback carries two headers so you can prove it came from Cradex — without relying on the api_key parameter alone:

Signature scheme

X-Cradex-Timestamp: <unix seconds>
X-Cradex-Signature: sha256=HMAC_SHA256(webhookSecret, timestamp + "." + trans_id + "." + status + "." + received)

The webhookSecret is shown next to your API key in the dashboard. Compare signatures in constant time and reject timestamps older than a few minutes to block replays.

<?php
// webhooks/cradex.php — xác minh chữ ký trước khi xử lý đơn
$secret    = getenv('CRADEX_WEBHOOK_SECRET');
$data      = $_SERVER['REQUEST_METHOD'] === 'POST' ? $_POST : $_GET;
$timestamp = $_SERVER['HTTP_X_CRADEX_TIMESTAMP'] ?? '';
$signature = $_SERVER['HTTP_X_CRADEX_SIGNATURE'] ?? '';

$payload  = $timestamp . '.' . $data['trans_id'] . '.' . $data['status'] . '.' . $data['received'];
$expected = 'sha256=' . hash_hmac('sha256', $payload, $secret);

// Chống replay: từ chối callback cũ hơn 5 phút
if (!hash_equals($expected, $signature) || abs(time() - (int) $timestamp) > 300) {
    http_response_code(401);
    exit('Invalid signature');
}

if ($data['status'] === 'completed') {
    // markOrderPaid($data['request_id'], $data['received'], $data['transaction_id']);
}

http_response_code(200); // chỉ 2xx mới được tính là thành công
echo 'OK';

Reference

Invoice statuses

waiting

Created, waiting for the customer to pay.

No callback

completed

The exact amount was received on-chain.

Callback sent

expired

Lifetime ended without payment, or cancelled.

Callback sent

The hosted checkout may briefly show confirming while the transaction gathers confirmations; the API reports it as waiting until it is final. Invoices cancelled from the dashboard are reported as expired.

Reference

Error messages

Errors return HTTP 200 with { "status": "error", "msg": "…" }. The messages are identical to NTPAY so existing integrations keep working.

msg	Cause
Please configure merchant_id	merchant_id is missing.
Please configure api_key	api_key is missing.
Merchant does not exist in the system	merchant_id or api_key is wrong.
This merchant is under maintenance	The merchant is disabled in your dashboard.
This merchant does not support the Crypto payment gateway	The merchant isn't set up for crypto payments.
This merchant does not have a wallet to receive money	Add and enable at least one receiving wallet.
User does not exist in the system	The owner account is locked or no longer exists.
Please enter the invoice name	name is missing.
Please enter the invoice description	description is missing.
Please enter the deposit amount	amount is missing.
The minimum amount is 1$	amount is below 1 USDT.
Please do not SPAM	More than 4 identical invoices (name + description + amount) are waiting.
Please enter the transaction ID	trans_id is missing (GetInvoiceStatus).
Invoice does not exist in the system	Unknown trans_id or it belongs to another merchant.

Reference

Rate limits & security

Wrong API key. More than 15 failed attempts per minute temporarily blocks the calling IP.
Duplicate invoices. At most 4 identical invoices (name + description + amount) can be waiting at the same time.
Minimum amount. 1 USDT per invoice.
Balance. The merchant owner must keep a positive USD balance to pay gateway fees.
Use trans_id. Always look invoices up by trans_id, not request_id.

Integrations

WooCommerce & WHMCS

Because the API is NTPAY-compatible, any existing NTPAY / USDT plugin for WooCommerce, WHMCS or HostBill works with Cradex. You only point it at our base URL.

WooCommerce

1Install your NTPAY-compatible USDT gateway plugin.
2WooCommerce → Settings → Payments → USDT.
3Set the API URL to https://cradex.net/api.
4Paste your merchant_id and api_key, then save.

WHMCS

1Upload the NTPAY-compatible gateway module to /modules/gateways.
2Setup → Payments → Payment Gateways → activate it.
3Set the API URL to https://cradex.net/api.
4Enter merchant_id and api_key; callbacks are configured automatically.

Using HostBill? Keep type=HostBill in your callback URL — Cradex will then deliver callbacks as a POST form, as HostBill expects.

Integrations

Migrating from NTPAY

Endpoints, parameters, responses, error messages and callback fields are identical. Migration is a one-line change:

config.php

// Before
$base_url = 'https://your-ntpay-domain.com';

// After
$base_url = 'https://cradex.net';

Create a merchant in Cradex and add your existing receiving wallets.
Replace merchant_id and api_key with your Cradex credentials.
Optionally verify the new X-Cradex-Signature header for stronger security.
Return HTTP 2xx from your callback handler so deliveries are marked successful.

Ready to integrate?

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