Klix Payment Gateway Integration

Integrate Klix (by Citadele) payment gateway into any web application or website. Klix supports card payments, Apple Pay, Google Pay, bank transfers (PIS) across the Baltics, and Pay Later installments.

Official docs: https://developers.klix.app/ Full API reference (OpenAPI): https://portal.klix.app/api/schema/v1/

Quick Start Checklist

Before integrating, confirm these with the user:

1. Credentials — Brand ID and Secret Key (from Klix merchant portal or test env)
2. Integration type — eCommerce plugin, widget library, or direct API?
3. Payment methods needed — cards, Apple Pay, Google Pay, bank PIS, Pay Later?
4. Payment scenarios — one-time, recurring, reservation/capture?

If unsure, start with the test environment to prototype.

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Test Environment

Use these credentials for development and testing:

Field	Value
Brand ID	702314b8-dd86-41fa-9a22-510fdd71fa92
Secret Key (full features)	IB-bzOdJLgJjbsaA34Qpxkg1TTIrW-iDuni6JuzbP--KgtsREHzvIvLLTH8E5T0CZcSbYM3qNmfeogpWW_RZaA==
Secret Key (simple)	No51P_Dq4jQGeha6_eQpfjAFe67u3QYHEO95jrcCux0zPfByd8x9poSa6xINQPz1hyUGKNYoxa16rnUkSUI_MA==

Test cards:

Type	PAN	CVV	Expiry	3DS Password
VISA	4505 1312 3400 0029	123	06/28	hint
Mastercard	5191 6312 3400 0024	583	06/28	hint

Any cardholder name is accepted. On the test payment page, choose "successful" or "failed" scenario.

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Integration Approaches

Choose based on the project:

1. eCommerce Plugin (no code)

For WooCommerce (3.5+), Shopify, Magento (2.0+), OpenCart (3.0+), PrestaShop (1.7+), Mozello. See references/ecommerce-plugins.md for platform-specific setup.

2. Frontend Widget (Pay Later only)

For showing monthly payment calculators on product/cart pages. See references/pay-later-widget.md.

3. @biggora/klix TypeScript SDK (recommended for Node.js / TypeScript)

Typed SDK wrapping the REST API with built-in caching, error types, signature verification, and first-class NestJS support. Dual ESM/CJS. Node.js 20+. See the SDK section below for details.

4. Direct API Integration (recommended for non-Node.js stacks)

Full control over payment flow via raw HTTP requests. Works with any language. See the API Reference section below.

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@biggora/klix SDK (Node.js / TypeScript)

Installation

npm install @biggora/klix

Client Setup

import { createKlixClient } from '@biggora/klix';

const klix = createKlixClient({
  apiKey: process.env.KLIX_API_KEY!,
  brandId: process.env.KLIX_BRAND_ID!,
});

Available Resources

Resource	Methods
klix.purchases	create, read, cancel, capture, charge, refund, release
klix.balance	get
klix.paymentMethods	list({ currency }) — 60s cache built-in
klix.clients	create, list, iterateAll, listRecurringTokens(clientId)
klix.billing	sendInvoice
klix.billingTemplates	create, list, addSubscriber, sendInvoice, listClients
klix.companyStatements	create, list
klix.webhooks	create, list, listDeliveries

brandId is auto-injected into paymentMethods.list() and purchase calls.

Purchase Example

const purchase = await klix.purchases.create({
  currency: 'EUR',
  reference: 'ORDER-1001',
  client: { email: 'customer@example.com' },
  purchase: {
    products: [{ name: 'Pro subscription', price: 1999, quantity: 1 }],
  },
  success_callback: 'https://example.com/api/klix/callback',
  success_redirect: 'https://example.com/checkout/success',
  failure_redirect: 'https://example.com/checkout/failure',
});
// Redirect customer to purchase.checkout_url

Error Handling

import { KlixApiError } from '@biggora/klix';

try {
  await klix.purchases.read('invalid-id');
} catch (err) {
  if (err instanceof KlixApiError) {
    console.error(err.status, err.code, err.message, err.details);
  }
}

Signature Verification

// Success callback verification
const valid = await klix.verifySuccessCallback(rawBodyBuffer, signatureHeader);

// Webhook payload verification
import { verifyWebhookPayload } from '@biggora/klix';
const valid = verifyWebhookPayload(rawBodyBuffer, signatureHeader, webhook.public_key);

NestJS Integration

Import from @biggora/klix/nestjs. Requires rawBody: true in NestFactory.

import { KlixModule } from '@biggora/klix/nestjs';

@Module({
  imports: [
    KlixModule.forRootAsync({
      inject: [ConfigService],
      useFactory: (config: ConfigService) => ({
        apiKey: config.getOrThrow('KLIX_API_KEY'),
        brandId: config.getOrThrow('KLIX_BRAND_ID'),
      }),
    }),
  ],
})
export class AppModule {}

Inject the client in services:

import { InjectKlixClient } from '@biggora/klix/nestjs';
import type { KlixClient } from '@biggora/klix';

@Injectable()
export class PaymentsService {
  constructor(@InjectKlixClient() private readonly klix: KlixClient) {}

  async createPayment(order: Order) {
    return this.klix.purchases.create({ /* ... */ });
  }
}

Use KlixSignatureVerifier for callback verification in controllers:

import { KlixSignatureVerifier } from '@biggora/klix/nestjs';

@Controller('klix')
export class KlixController {
  constructor(private readonly verifier: KlixSignatureVerifier) {}

  @Post('callback')
  async callback(@Req() req: RawBodyRequest<Request>) {
    const valid = await this.verifier.verifySuccessCallback(
      req.rawBody ?? Buffer.alloc(0),
      String(req.headers['x-signature'] ?? ''),
    );
    if (valid) {
      // process the payment
    }
    return { ok: true };
  }
}

---

API Reference (Direct HTTP)

If using @biggora/klix SDK, these endpoints are handled automatically. This section is for direct HTTP integration with non-Node.js stacks.

Base URL: https://portal.klix.app/api/v1/

Authentication: Bearer token in the Authorization header:

Authorization: Bearer <Secret Key>

Required headers for all requests:

Accept: application/json
Content-Type: application/json
Authorization: Bearer <SECRET_KEY>

Amounts are always in cents (e.g., 3000 = 30.00 EUR).

Core Endpoints

List Available Payment Methods

GET /payment_methods/?currency=EUR&brand_id=<BRAND_ID>

Returns available methods with names, logos, country availability. Cache this response — rate-limited to max 1 request/minute.

Create a Purchase

POST /purchases/

Minimal request body:

{
  "brand_id": "<BRAND_ID>",
  "success_callback": "https://yoursite.com/api/klix/callback",
  "success_redirect": "https://yoursite.com/order/success",
  "failure_redirect": "https://yoursite.com/order/failure",
  "cancel_redirect": "https://yoursite.com/order/cancel",
  "purchase": {
    "language": "en",
    "products": [
      {
        "name": "Product name",
        "price": 2999
      }
    ]
  },
  "client": {
    "email": "customer@example.com"
  },
  "reference": "ORDER-123"
}

Response includes id (purchase ID) and checkout_url — redirect the customer there.

Get Purchase Status

GET /purchases/<PURCHASE_ID>/

Capture Reserved Funds

POST /purchases/<PURCHASE_ID>/capture/

Optional body for partial capture: {"amount": 1500}

Release Reserved Funds

POST /purchases/<PURCHASE_ID>/release/

Charge Recurring Payment

POST /purchases/<PURCHASE_ID>/charge

Body: {"recurring_token": "<TOKEN>"}

Payment Flow

1. Server: POST /purchases/ → get checkout_url
2. Client: Redirect customer to checkout_url
3. Customer: Completes payment on Klix page
4. Klix: POST to success_callback (server-to-server)
5. Klix: Redirect customer to success_redirect or failure_redirect
6. Server: Verify payment via GET /purchases/<ID>/

Always verify payment status server-side via the callback. Do not rely solely on the redirect.

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Payment Scenarios

One-Time Payment

Standard flow as shown above. No extra parameters needed.

Recurring Payments

1. Create initial purchase with "force_recurring": true
2. On success callback, store the purchase id as the recurring token
3. For subsequent charges: create a new purchase, then call /charge with the token

{
  "brand_id": "<BRAND_ID>",
  "force_recurring": true,
  "success_callback": "https://yoursite.com/api/klix/callback",
  "success_redirect": "https://yoursite.com/success",
  "failure_redirect": "https://yoursite.com/failure",
  "purchase": {
    "products": [{"name": "Subscription", "price": 999}]
  },
  "client": {"email": "user@example.com"}
}

Reservation (Authorization Hold)

1. Create purchase with "skip_capture": true
2. Funds are held (status: "hold")
3. Later: capture full/partial amount or release
4. Auto-releases after 6 days if not captured

Restrict Payment Methods

Use payment_method_whitelist to show only specific methods:

{
  "payment_method_whitelist": ["klix", "klix_apple_pay", "klix_google_pay"]
}

Native Apple Pay / Google Pay

1. Create purchase with payment_method_whitelist: ["klix_apple_pay"] (or klix_google_pay)
2. Get encrypted token from Apple/Google Pay JS API
3. POST to https://portal.klix.app/api/v1/p/<PURCHASE_ID>/
   • Form data: pm=klix_apple_pay, s2s=true, token=<Base64_token>
4. If response contains threeDsRedirectUrl, redirect customer for 3DS verification

Apple Pay detection: window.ApplePaySession && ApplePaySession.canMakePayments()

Bulk Payments (PIS)

Supported on: citadele_*_pis, seb_*_pis, swedbank_*_pis Include payment_method_details.pis_bulk_purchase[] with creditor IBAN, name, amount, reference. All IBANs must be pre-whitelisted with Klix.

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Supported Payment Methods

See references/payment-methods.md for the full list of 24 methods across Latvia, Lithuania, and Estonia.

Key method IDs:

• klix — Card payments (Visa, Mastercard)
• klix_apple_pay — Apple Pay
• klix_google_pay — Google Pay
• klix_pay_later — Installments
• *_pis — Bank transfers (e.g., swedbank_lv_pis, seb_ee_pis)
• *_digilink — Citadele bank links

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Callback Handling

Klix sends a server-to-server POST to success_callback when payment completes. Implement a POST endpoint that:

1. Receives the callback
2. Verifies payment by calling GET /purchases/<ID>/
3. Updates order status in your database
4. Returns HTTP 200

Example (Node.js/Express):

app.post('/api/klix/callback', async (req, res) => {
  const purchaseId = req.body.id;
  const response = await fetch(
    `https://portal.klix.app/api/v1/purchases/${purchaseId}/`,
    { headers: { 'Authorization': `Bearer ${process.env.KLIX_SECRET_KEY}` } }
  );
  const purchase = await response.json();
  if (purchase.status === 'paid') {
    await updateOrderStatus(purchase.reference, 'paid');
  }
  res.sendStatus(200);
});

Using @biggora/klix SDK:

import { createKlixClient } from '@biggora/klix';

const klix = createKlixClient({
  apiKey: process.env.KLIX_SECRET_KEY,
  brandId: process.env.KLIX_BRAND_ID,
});

app.post('/api/klix/callback', async (req, res) => {
  const valid = await klix.verifySuccessCallback(
    req.rawBody, req.headers['x-signature']
  );
  if (valid) {
    const purchase = await klix.purchases.read(req.body.id);
    if (purchase.status === 'paid') {
      await updateOrderStatus(purchase.reference, 'paid');
    }
  }
  res.sendStatus(200);
});

Note: enable raw body parsing (express.raw() or { rawBody: true } in NestJS) for signature verification.

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Branding Guidelines

• Show Klix logo alongside other payment methods in footer and checkout
• Use official button assets from https://developers.klix.app/static-assets/
• Checkout button labels by language (LV/EN/LT/RU) — see references/branding.md
• Apple Pay: follow Apple's representation guidelines
• Contact marketing@klix.app for custom landing page text changes

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Reference Files

Read these for deeper details on specific topics:

• references/payment-methods.md — Full list of 24 payment methods with country/validation details
• references/pay-later-widget.md — Frontend widget for installment calculator display
• references/ecommerce-plugins.md — Platform-specific plugin setup (WooCommerce, Shopify, etc.)
• references/branding.md — Logo assets, button labels, landing page requirements

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Common Integration Patterns

Next.js / React

1. npm install @biggora/klix
2. Create API route POST /api/checkout — use klix.purchases.create(), return checkout_url
3. Create API route POST /api/klix/callback — use klix.verifySuccessCallback() + klix.purchases.read()
4. Redirect to checkout_url from client via router.push()
5. Create success/failure/cancel pages

Express / Node.js

1. npm install @biggora/klix
2. Initialize client: createKlixClient({ apiKey, brandId })
3. POST /checkout — klix.purchases.create(...), return checkout_url
4. POST /webhook/klix — klix.verifySuccessCallback(), then klix.purchases.read()
5. GET /order/:id/status — klix.purchases.read(id)

NestJS

1. npm install @biggora/klix
2. Import KlixModule.forRootAsync() in AppModule with ConfigService
3. Inject KlixClient via @InjectKlixClient() in payment services
4. Use KlixSignatureVerifier in webhook controller
5. Enable rawBody: true in NestFactory.create()

PHP / Laravel

1. Use klix/klix-sdk-php from Packagist (official SDK)
2. Create checkout controller
3. Add webhook route for callback

Any Other Stack

1. Make HTTP requests to the API directly (see API Reference section)
2. Or generate a client from the OpenAPI schema: https://portal.klix.app/api/schema/v1/