v1.0 · StableNowPayments-compatible

Nowpay API Reference

Accept USDT payments on BSC, Polygon, Arbitrum, Optimism, and Base. Samex-api-keyauthentication as NowPayments, REST verbs, and IPN-style webhooks — drop-in compatible for most integrations.

Open Swagger UI Download OpenAPI JSON

Introduction

The Nowpay API is a RESTful HTTP API secured by anx-api-keyheader — the same convention used by NowPayments. Every response is JSON; every error follows the{ error: { code, message } }envelope.

Nowpay is purpose-built for USDT-only settlement across five EVM networks: BSC, Polygon, Arbitrum, Optimism, and Base. This narrower scope allows lower fees (from $0.10/payout), instant finality, and a single integration surface — versus NowPayments' 300+ coins.

All write endpoints support idempotency keys via theIdempotency-Keyheader (required for payouts and swaps). Real-time updates are pushed via signed webhooks and socket.io events.

Base URL

https://nowpay.finance/api/v1

Swagger UI

/api/docs

Authentication

Every request must include an API key. Nowpay accepts both common conventions — pick whichever your existing code uses:

NowPayments-stylerecommended

x-api-key: sk_live_...

Same header name as NowPayments — zero code change for migrating merchants.

Bearer (RFC 6750)

Authorization: Bearer sk_live_...

Nowpay-native. Use this if you already have a Bearer-token HTTP client.

Getting an API key

Sign up at /dashboard/signup and complete KYB.
Wait for admin approval (typically < 24 h). Until then, API calls return 403 kyb_required.
Open Dashboard → API Keys → Generate new key.
Choose scopes: invoice, payout, swap.
Copy the key immediately — the full key is shown only once (prefix is stored for later identification).

Rate limiting

60 requests/min per API key (sliding window). Every response includes these headers:

response-headers

X-RateLimit-Limit:     60
X-RateLimit-Remaining: 58
X-RateLimit-Reset:      1738368240

Quick start

Create an invoice in three languages. The flow is identical in all three — POST to/api/v1/invoices, get back a checkout_url, redirect your customer.

cURL

quickstart.sh

# 1. Create an invoice
curl -X POST https://nowpay.finance/api/v1/invoices \
  -H "x-api-key: sk_live_4f3c2b1a9e8d7c6b5a4f3e2d1c0b9a8f" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: $(uuidgen)" \
  -d '{
    "amount": "50.00",
    "network": "polygon",
    "external_id": "order_12345",
    "success_url": "https://shop.example.com/thanks"
  }'

# 2. Redirect your customer to checkout_url from the response.
# 3. Receive a webhook at your ipn_callback_url when the payment is confirmed.

JavaScript (Node 18+)

quickstart.mjs

// Node 18+ (built-in fetch). For browsers, use the same code in a <script type="module">.
const res = await fetch("https://nowpay.finance/api/v1/invoices", {
  method: "POST",
  headers: {
    "x-api-key": process.env.NOWPAY_API_KEY,
    "Content-Type": "application/json",
    "Idempotency-Key": crypto.randomUUID(),
  },
  body: JSON.stringify({
    amount: "50.00",
    network: "polygon",
    external_id: "order_12345",
    success_url: "https://shop.example.com/thanks",
  }),
});

const invoice = await res.json();
console.log(invoice.checkout_url);
// → https://nowpay.finance/i/inv_abc123

Python

quickstart.py

import requests, uuid

API_KEY = "sk_live_4f3c2b1a9e8d7c6b5a4f3e2d1c0b9a8f"

res = requests.post(
    "https://nowpay.finance/api/v1/invoices",
    headers={
        "x-api-key": API_KEY,
        "Content-Type": "application/json",
        "Idempotency-Key": str(uuid.uuid4()),
    },
    json={
        "amount": "50.00",
        "network": "polygon",
        "external_id": "order_12345",
        "success_url": "https://shop.example.com/thanks",
    },
)
res.raise_for_status()
invoice = res.json()
print(invoice["checkout_url"])
# → https://nowpay.finance/i/inv_abc123

Invoices

An invoice represents a single payment request — generated deposit address, amount, network, expiry. The customer sends USDT to the address; once the chain finality threshold is reached, the invoice flips to finished and the amount is credited to the merchant's ledger balance for that chain.

POST/api/v1/invoices≡ NowPayments POST /v1/invoice

Create an invoice

Creates a payment invoice for the requested amount on the requested chain. Nowpay generates an HD-derived deposit address (BIP44 m/44'/60'/0'/0/<index>), queues an invoice.waiting webhook, and returns the hosted checkout URL your customer can be redirected to. The deposit address is unique per invoice — never reused.

Parameter	Type	Required	Description
amount	string	yes	USDT amount (e.g. "50.00"). Numeric string — never a JS number.
network	string	yes	One of: bsc, polygon, arbitrum, optimism, base.
external_id	string	no	Merchant-internal order ID for reconciliation.
success_url	string	no	Redirect URL after successful payment.
cancel_url	string	no	Redirect URL after cancellation/timeout.
metadata	object	no	Arbitrary JSON metadata stored with the invoice.

Request example

request.sh

curl -X POST https://nowpay.finance/api/v1/invoices \
  -H "x-api-key: sk_live_4f3c2b1a9e8d7c6b5a4f3e2d1c0b9a8f" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: 9b1c2d3e-4f5a-6b7c-8d9e-0f1a2b3c4d5e" \
  -d '{
    "amount": "50.00",
    "network": "polygon",
    "external_id": "order_12345",
    "success_url": "https://shop.example.com/thanks",
    "cancel_url": "https://shop.example.com/cart"
  }'

Response example

response.json

{
  "id": "inv_abc123",
  "status": "waiting",
  "address": "0x7d5a3f9c2b1e8a4d6f0c2b5a7e9d1f3c4b2a8e6d",
  "amount": "50.00",
  "network": "polygon",
  "expires_at": "2026-01-01T12:00:00.000Z",
  "checkout_url": "https://nowpay.finance/i/inv_abc123"
}

Error codes

Code	Status	Description
invalid_amount	400	amount missing or not a positive numeric string.
invalid_network	400	network is not a supported chain code.
network_inactive	400	chain exists in config but is not active.
idempotency_conflict	409	Idempotency-Key reused with a different body.

GET/api/v1/invoices?id={id}≡ NowPayments GET /v1/invoice/{id}

Get invoice by ID

Returns the current state of a single invoice — including the deposit address, paid amount (which may differ from the requested amount if the customer over/underpaid), and the on-chain transaction hash once confirmed.

Parameter	Type	Required	Description
id	string	yes	Invoice ID returned by POST /api/v1/invoices.

Request example

request.sh

curl https://nowpay.finance/api/v1/invoices?id=inv_abc123 \
  -H "x-api-key: sk_live_4f3c2b1a9e8d7c6b5a4f3e2d1c0b9a8f"

Response example

response.json

{
  "id": "inv_abc123",
  "status": "finished",
  "amount": "50.00",
  "paidAmount": "50.00",
  "network": "polygon",
  "address": "0x7d5a3f9c2b1e8a4d6f0c2b5a7e9d1f3c4b2a8e6d",
  "expiresAt": "2026-01-01T12:00:00.000Z",
  "overpaid": false,
  "createdAt": "2026-01-01T11:00:00.000Z",
  "externalId": "order_12345"
}

Error codes

Code	Status	Description
not_found	404	No invoice with that ID belongs to this merchant.

GET/api/v1/invoices?limit=50&cursor={cursor}≡ NowPayments GET /v1/invoice

List invoices

Returns a paginated list of the merchant's invoices, newest first. Use the `next_cursor` from the previous response to fetch the next page. When `next_cursor` is `null`, you've reached the end.

Parameter	Type	Required	Description
limit	integer	no	Page size. Default 50, max 100.
cursor	string	no	Opaque cursor from `next_cursor` of the previous page.
status	string	no	Filter by status: waiting \| confirming \| finished \| expired \| refunded.

Request example

request.sh

curl "https://nowpay.finance/api/v1/invoices?limit=10&status=finished" \
  -H "x-api-key: sk_live_4f3c2b1a9e8d7c6b5a4f3e2d1c0b9a8f"

Response example

response.json

{
  "data": [
    {
      "id": "inv_abc123",
      "externalId": "order_12345",
      "amount": "50.00",
      "status": "finished",
      "network": "polygon",
      "address": "0x7d5a3f9c2b1e8a4d6f0c2b5a7e9d1f3c4b2a8e6d",
      "createdAt": "2026-01-01T11:00:00.000Z",
      "expiresAt": "2026-01-01T12:00:00.000Z"
    }
  ],
  "next_cursor": null
}

Payouts

A payout sends USDT from your merchant balance to a beneficiary address. The payout saga is:lock → sign/broadcast → confirm. Funds are locked the moment you POST. If the amount is below your autoApproveLimit(default 100 USDT), broadcast happens automatically. Above that, an admin must approve — and above 1,000 USDT the admin must complete a 2FA challenge.

POST/api/v1/payouts≡ NowPayments POST /v1/payout

Create a payout

Requests a USDT payout to a beneficiary address. The Idempotency-Key header is **required** — without it, the request is rejected with 400. Funds are locked immediately via a double-entry ledger transaction. If the amount is at or below the merchant's `autoApproveLimit` (default 100 USDT), the payout saga runs automatically. Otherwise it enters `pending_review` and an admin must approve (with 2FA for amounts above the 1,000 USDT threshold).

Parameter	Type	Required	Description
amount	string	yes	USDT to send (e.g. "100.00"). Must be ≥ chain.min_payout.
network	string	yes	bsc \| polygon \| arbitrum \| optimism \| base.
address	string	yes	Beneficiary EVM address (0x...). Must be whitelisted if require_whitelist is on.
Idempotency-Key	header	yes	Replay-safe key (UUIDv4). Required.

Request example

request.sh

curl -X POST https://nowpay.finance/api/v1/payouts \
  -H "x-api-key: sk_live_4f3c2b1a9e8d7c6b5a4f3e2d1c0b9a8f" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: c0a1b2c3-d4e5-6f7a-8b9c-0d1e2f3a4b5c" \
  -d '{
    "amount": "100.00",
    "network": "polygon",
    "address": "0xRecipientAddress"
  }'

Response example

response.json

{
  "id": "po_xyz789",
  "status": "approved",
  "fee_network": "0.5029",
  "gas_estimate_usdt": "0.0023",
  "gas_charged_usdt": "0.0029",
  "platform_fee_usdt": "0.50",
  "amount": "100.00",
  "network": "polygon",
  "address": "0xRecipientAddress",
  "created_at": "2026-01-01T12:30:00.000Z"
}

Error codes

Code	Status	Description
missing_idempotency_key	400	Idempotency-Key header is required for payouts.
below_minimum	400	amount is below chain.min_payout (e.g. < 1 USDT on polygon).
invalid_address	400	Not a valid EVM address.
address_not_whitelisted	403	require_whitelist is on and this address is not whitelisted.
emergency_stop_active	403	Payouts are frozen for this account. Contact support.
insufficient_balance_polygon	409	Not enough available USDT on that chain (includes fee breakdown).
daily_limit_exceeded	409	Sum of today's payouts exceeds dailyLimit.
payouts_frozen	409	Reconciliation detected a divergence — payouts are globally frozen.

GET/api/v1/payouts/estimate?network={code}&amount={amount}≡ NowPayments GET /v1/estimated-price

Estimate payout fees

Previews the fee breakdown before committing to a payout. Gas prices are cached for 30 s; the +20% padding absorbs drift between this call and the subsequent POST /api/v1/payouts. Use this to show a transparent fee breakdown to your end-user.

Parameter	Type	Required	Description
network	string	yes	Chain code (bsc, polygon, etc.).
amount	string	yes	USDT amount (e.g. "100.50").

Request example

request.sh

curl "https://nowpay.finance/api/v1/payouts/estimate?network=polygon&amount=100.00" \
  -H "x-api-key: sk_live_4f3c2b1a9e8d7c6b5a4f3e2d1c0b9a8f"

Response example

response.json

{
  "network": "polygon",
  "amount": "100.00",
  "gas_estimate_usdt": "0.0023",
  "gas_charged_usdt": "0.0029",
  "platform_fee_usdt": "0.50",
  "fee_network_total": "0.5029",
  "total_debited": "100.5029",
  "beneficiary_receives": "100.00",
  "meta": {
    "gas_token": "POL",
    "gas_token_amount": "0.000003",
    "gas_price_wei": "50000000",
    "gas_units": "60000",
    "padding_bps": 2000,
    "markup_bps": 500,
    "payout_fee_fixed": "0.50",
    "payout_fee_bps": 0,
    "gas_price_cached": true,
    "token_price_cached": true,
    "token_price_fallback": false
  }
}

GET/api/v1/payouts?status={status}&limit=50≡ NowPayments GET /v1/payout

List payouts

Returns the merchant's payouts (newest first).

Parameter	Type	Required	Description
status	string	no	pending_review \| approved \| broadcasting \| sent \| failed \| rejected.
limit	integer	no	Default 50, max 100.

Request example

request.sh

curl "https://nowpay.finance/api/v1/payouts?status=sent" \
  -H "x-api-key: sk_live_4f3c2b1a9e8d7c6b5a4f3e2d1c0b9a8f"

Response example

response.json

{
  "data": [
    {
      "id": "po_xyz789",
      "status": "sent",
      "amount": "100.00",
      "fee_network": "0.5029",
      "network": "polygon",
      "address": "0xRecipientAddress",
      "txid": "0xdef456...",
      "created_at": "2026-01-01T12:30:00.000Z",
      "sent_at": "2026-01-01T12:30:45.000Z",
      "error": null
    }
  ]
}

Balance

Nowpay uses a double-entry ledger. Each chain has its own balance bucket — BSC USDT and Polygon USDT are not fungible. To move between them, usePOST /api/v1/swaps.

GET/api/v1/balance≡ NowPayments GET /v1/balance

Get merchant balance

Returns the merchant's available and locked USDT balances. Nowpay uses a per-chain ledger — BSC USDT and Polygon USDT are NOT fungible. To move between chains, use POST /api/v1/swaps.

Request example

request.sh

curl https://nowpay.finance/api/v1/balance \
  -H "x-api-key: sk_live_4f3c2b1a9e8d7c6b5a4f3e2d1c0b9a8f"

Response example

response.json

{
  "total": "1250.00",
  "locked": "100.00",
  "by_network": {
    "bsc": "250.00",
    "polygon": "1000.00"
  },
  "by_network_locked": {
    "bsc": "0",
    "polygon": "100.00"
  }
}

Networks

Lists the supported EVM chains with their USDT contract addresses, finality thresholds, and payout fee configuration. Use this to populate a chain picker in your checkout UI.

GET/api/v1/networks≡ NowPayments GET /v1/currencies

List supported networks

Returns all active EVM chains, their USDT contract addresses, confirmation thresholds, and per-chain payout fee configuration. Use this to populate a chain picker in your checkout UI.

Request example

request.sh

curl https://nowpay.finance/api/v1/networks \
  -H "x-api-key: sk_live_4f3c2b1a9e8d7c6b5a4f3e2d1c0b9a8f"

Response example

response.json

{
  "networks": [
    {
      "code": "bsc",
      "name": "BNB Smart Chain",
      "chain_id": 56,
      "usdt_contract": "0x55d398326f99059fF775485246999027B3197955",
      "decimals": 18,
      "gas_token": "BNB",
      "confirmations": 12,
      "finality_strategy": "block_count",
      "is_premium": false,
      "payout_fee_fixed": "0.50",
      "payout_fee_bps": 0,
      "min_payout": "1.00",
      "hot_wallet_treshold": "5000.00"
    },
    {
      "code": "polygon",
      "name": "Polygon PoS",
      "chain_id": 137,
      "usdt_contract": "0xc2132D05D31c914a87C6611C10748AEb04B58e8F",
      "decimals": 6,
      "gas_token": "POL",
      "confirmations": 10,
      "finality_strategy": "block_count",
      "is_premium": false,
      "payout_fee_fixed": "0.50",
      "payout_fee_bps": 0,
      "min_payout": "1.00",
      "hot_wallet_treshold": "5000.00"
    }
  ]
}

Swaps

Cross-chain USDT swaps are ledger-only (no on-chain DEX). 0.5% fee (50 bps). Subject to a liquidity guard — the destination treasury hot wallet must hold sufficient USDT.

POST/api/v1/swaps

Cross-chain USDT swap

Converts USDT from one chain to another via a ledger-only transfer (no on-chain DEX). Subject to a 0.5% swap fee (50 bps) and a liquidity guard — the destination chain treasury hot wallet must hold sufficient USDT. Idempotency-Key header is **required**. NowPayments has no direct equivalent (it treats each coin as independent).

Parameter	Type	Required	Description
from_network	string	yes	Source chain (e.g. "bsc").
to_network	string	yes	Destination chain (must differ from from_network).
amount	string	yes	USDT to swap (e.g. "100.00").
Idempotency-Key	header	yes	Replay-safe key (UUIDv4).

Request example

request.sh

curl -X POST https://nowpay.finance/api/v1/swaps \
  -H "x-api-key: sk_live_4f3c2b1a9e8d7c6b5a4f3e2d1c0b9a8f" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: 7e8f9a0b-1c2d-3e4f-5a6b-7c8d9e0f1a2b" \
  -d '{
    "from_network": "bsc",
    "to_network": "polygon",
    "amount": "100.00"
  }'

Response example

response.json

{
  "id": "sw_abc12345",
  "fee": "0.50",
  "status": "done",
  "from_network": "bsc",
  "to_network": "polygon",
  "amount": "100.00"
}

Error codes

Code	Status	Description
missing_idempotency_key	400	Idempotency-Key header is required for swaps.
same_network	400	from_network and to_network must differ.
insufficient_balance_bsc	409	Not enough USDT on the source chain.

Webhooks

Nowpay delivers event notifications to the URL you register in the merchant dashboard (Webhooks tab). Each delivery includes:

Header	Description
X-Signature	HMAC-SHA256(rawBody, secret). Hex. Nowpay-native.
x-nowpayments-sig	HMAC-SHA512(rawBody, secret). Hex. NowPayments-compatible.
X-Timestamp	Unix seconds at send time. Anti-replay: reject if `\|now - X-Timestamp\| > 300`.
X-Event	Event name (e.g. `invoice.finished`).

Event types

invoice.waiting

invoice.confirming

invoice.finished

invoice.expired

deposit.credited

payout.pending_review

payout.approved

payout.broadcasting

payout.sent

payout.failed

swap.done

treasury.gas_low

Example payload

webhook-payload.json

{
  "event": "invoice.finished",
  "data": {
    "invoiceId": "inv_abc123",
    "merchantId": "mer_xyz",
    "network": "polygon",
    "amount": "50.00",
    "address": "0x7d5a3f9c2b1e8a4d6f0c2b5a7e9d1f3c4b2a8e6d",
    "paid_amount": "50.00",
    "txid": "0xabc123def456...",
    "overpaid": false
  },
  "timestamp": "2026-01-01T12:05:30.000Z"
}

Retry policy

Failed deliveries (non-2xx or network error) are retried with exponential backoff:

retry-schedule

1m → 10m → 1h → 6h → 24h  (5 attempts total)

Signature verification (Node.js)

verify-webhook.ts

import crypto from "node:crypto"

/**
 * Verify an incoming Nowpay webhook signature.
 *
 * Nowpay sends TWO signatures on every webhook delivery — both computed
 * over the EXACT raw body bytes (do NOT re-serialize JSON, key order matters):
 *   - X-Signature:        HMAC-SHA256(rawBody, secret).toString("hex")
 *   - x-nowpayments-sig:  HMAC-SHA512(rawBody, secret).toString("hex")
 *
 * Merchants migrating from NowPayments can keep their existing
 * x-nowpayments-sig verification code verbatim.
 *
 * Anti-replay: X-Timestamp (Unix seconds) — reject if older than 5 minutes.
 */
export function verifyNowpayWebhook({
  rawBody,
  headers,
  secret,
}: {
  rawBody: string
  headers: Record<string, string | undefined>
  secret: string
}): boolean {
  // 1. Anti-replay: reject timestamps older than 5 minutes
  const ts = Number(headers["x-timestamp"])
  if (!ts || Math.abs(Date.now() / 1000 - ts) > 300) {
    return false
  }

  // 2. Verify EITHER signature (Nowpay-native OR NowPayments-compatible)
  const expectedSha256 = crypto
    .createHmac("sha256", secret)
    .update(rawBody)
    .digest("hex")

  const expectedSha512 = crypto
    .createHmac("sha512", secret)
    .update(rawBody)
    .digest("hex")

  const sigA = headers["x-signature"] ?? ""
  const sigB = headers["x-nowpayments-sig"] ?? ""

  return (
    crypto.timingSafeEqual(Buffer.from(sigA), Buffer.from(expectedSha256)) ||
    crypto.timingSafeEqual(Buffer.from(sigB), Buffer.from(expectedSha512))
  )
}

Signature verification (Python)

verify_webhook.py

import hmac, hashlib, time

def verify_nowpay_webhook(raw_body: bytes, headers: dict, secret: str) -> bool:
    """Verify an incoming Nowpay webhook signature.

    Nowpay sends two signatures on every delivery — both HMAC of the exact
    raw body bytes (do NOT re-serialize JSON). Merchants migrating from
    NowPayments can keep their existing x-nowpayments-sig verification code.
    """
    # 1. Anti-replay: reject timestamps older than 5 minutes
    ts = int(headers.get("x-timestamp", "0"))
    if abs(time.time() - ts) > 300:
        return False

    # 2. Verify EITHER signature
    expected_sha256 = hmac.new(
        secret.encode(), raw_body, hashlib.sha256
    ).hexdigest()
    expected_sha512 = hmac.new(
        secret.encode(), raw_body, hashlib.sha512
    ).hexdigest()

    sig_a = headers.get("x-signature", "")
    sig_b = headers.get("x-nowpayments-sig", "")

    return (
        hmac.compare_digest(sig_a, expected_sha256)
        or hmac.compare_digest(sig_b, expected_sha512)
    )

Errors

All errors use the same envelope:

error-envelope.json

{
  "error": {
    "code": "invalid_amount",
    "message": "amount must be a numeric string"
  }
}

HTTP status	Meaning
200 / 201 / 202	Success (OK / Created / Accepted).
400	Bad request — invalid body, missing required field.
401	Missing or invalid API key.
403	Insufficient scope, KYB not approved, address not whitelisted, or emergency stop active.
404	Resource not found (or doesn't belong to this merchant).
409	Conflict — insufficient balance, daily limit exceeded, payouts frozen, or idempotency-key reuse with different body.
429	Rate limit exceeded. See `X-RateLimit-Reset` and `Retry-After` headers.
500	Internal error — retry with backoff. If persistent, contact support.

Migrating from NowPayments

Nowpay was designed so a NowPayments merchant can migrate in an afternoon. Below is the field-by-field mapping. The two big changes: (1) Nowpay uses plural endpoint paths(/api/v1/invoices vs NowPayments'/v1/invoice), and (2) Nowpay requires anIdempotency-Key header on payouts and swaps.

NowPayments	Nowpay	Note
x-api-key	x-api-key	Same header name. ✅ zero change.
POST /v1/invoice	POST /api/v1/invoices	Add `/api` prefix + pluralize.
price_amount	amount	String (NowPayments accepts number — we require string for decimal precision).
price_currency	— (always usd)	Nowpay only settles in USDT — no concept of fiat price.
pay_currency	network	Use chain code: bsc \| polygon \| arbitrum \| optimism \| base.
order_id	external_id	Same purpose — merchant-internal order ID.
ipn_callback_url	— (configured in dashboard)	Nowpay uses the dashboard-registered webhook URL; per-invoice override is on the roadmap.
pay_address	address	Same HD-derived deposit address. Just renamed.
x-nowpayments-sig (SHA-512)	x-nowpayments-sig (SHA-512)	Same header + algorithm — Nowpay also emits X-Signature (SHA-256) as native.
300+ coins	USDT only	Scope reduction — much lower fees, faster finality.
No idempotency	Idempotency-Key required	For payouts & swaps. Strongly recommended for invoices.

Before / after

migration-diff.sh

# Before (NowPayments):
curl -X POST https://api.nowpayments.io/v1/invoice \
  -H "x-api-key: $NOWPAYMENTS_KEY" \
  -d '{"price_amount": 50, "price_currency": "usd", "pay_currency": "usdt"}'

# After (Nowpay) — same auth header, same JSON shape philosophy:
curl -X POST https://nowpay.finance/api/v1/invoices \
  -H "x-api-key: $NOWPAY_KEY" \
  -H "Idempotency-Key: $(uuidgen)" \
  -d '{"amount": "50.00", "network": "polygon"}'

What's the same

Auth header name (x-api-key)
REST verbs (POST/GET)
JSON request/response
IPN webhook pattern
Hosted checkout page concept
Error envelope shape
Webhook signature algorithm (HMAC-SHA512 via x-nowpayments-sig)

What's different

Endpoint paths pluralized + /api prefix
USDT-only (5 EVM networks vs 300+ coins)
Field names: amount/network vs price_amount/pay_currency
Per-chain ledger balances (BSC USDT ≠ Polygon USDT)
Idempotency-Key required on payouts + swaps
2FA on large payouts (admin approval flow)
Webhook URL is dashboard-configured (not per-invoice)

Ready to integrate?

Open the interactive Swagger UI to send real test requests against your sandbox account, or download the OpenAPI 3.0 spec to generate a client in any language.

Swagger UI OpenAPI JSON