Kustom is about owning more of the checkout.

Kustom is an embedded checkout provider that grew out of Klarna Checkout and became an independent company in 2024. It offers a single-integration checkout covering card payments, Klarna Pay Later, Swish, Apple Pay, bank transfers, and a growing list of local payment methods across the Nordics and Europe. For ecommerce merchants who want a full checkout experience — not just a payment gateway — Kustom replaces the platform's native checkout with an embedded iframe that handles address collection, shipping selection, and payment in one flow.

But embedding a third-party checkout inside your ecommerce platform introduces its own set of delivery considerations. How Kustom interacts with your product data, shipping logic, and order management depends on the platform you choose and the surrounding architecture.

Where Kustom sits in the stack

Unlike a payment gateway that plugs into an existing checkout, Kustom replaces the checkout step entirely. The customer enters the Kustom iframe at the point of payment, and Kustom handles address entry, payment method selection, and order confirmation. Pre-filled customer data and address autocomplete reduce friction for returning shoppers.

This means the ecommerce platform needs to hand off cart data, shipping options, and discount calculations to Kustom at the right moment — and receive order confirmation, payment status, and customer data back. The handshake between platform and Kustom is where implementation complexity shows up. Product rules, shipping logic, and promotional pricing all need to arrive in the iframe correctly.

Everything before checkout — catalogue, pricing, cart — and everything after — order management, fulfilment, returns, settlement — stays with the ecommerce platform and the ERP.

Kustom across platforms

On Norce, Kustom integrates as an embedded checkout within the commerce layer. Norce's strength in complex product data and multi-market setups means the integration needs to handle customer-specific pricing, B2B buyer identification, and potentially multiple checkout configurations per market.

On Shopware, Kustom connects through the payment extension layer. Shopware's flexible checkout architecture gives control over how cart data reaches the Kustom iframe and how order states map back. For merchants with complex promotional rules or multi-language setups, the integration work is heavier than a standard payment plugin swap.

On Magento/Hyvä, Kustom has a mature extension with broad feature support — reflecting its Klarna Checkout heritage. The module replaces Magento's native checkout with the Kustom iframe and handles B2B mode, shipping integration, and order synchronisation. Hyvä's lightweight frontend improves page performance around the checkout, but the payment flow itself runs through Kustom's layer.

The pattern across platforms: Kustom's checkout works as designed, but how well it performs depends on how accurately the platform passes cart data, shipping options, and buyer context into the iframe — and how cleanly order data flows back.

Kustom's checkout model vs. traditional payment gateways

A traditional payment gateway handles only the payment step. The merchant builds the checkout UI, collects the address, presents shipping options, and then sends the customer to the gateway for payment authorisation. Kustom takes over the full checkout experience. The merchant sends cart data, and Kustom handles the rest.

The upside: high conversion potential. Pre-filled data, familiar UI for Nordic shoppers, and all payment methods in one place. The trade-off: less control over the checkout design and flow. If your store needs a highly customised checkout — conditional fields, complex shipping logic rendered inside the checkout, or deep personalisation — the iframe model constrains what you can do compared to building checkout natively on the platform.

This is a genuine architectural decision, not a small configuration choice. It affects frontend development, QA, and how edge cases (discount codes, mixed carts, subscription items) behave during checkout.

B2B and B2C in the same checkout

Kustom supports B2B mode, allowing merchants to serve both business and consumer buyers from the same store. Business buyers can enter company details and receive B2B payment methods like invoice. The toggle between B2C and B2B is configured at the integration level, and the checkout adapts the available payment methods and fields accordingly.

For this to work, the ecommerce platform needs to correctly pass buyer type information to Kustom. If the platform cannot distinguish between B2C and B2B sessions reliably, the wrong payment methods may appear — or the B2B toggle may not function as expected.

Kustom and the ERP connection

Payment events from Kustom — authorisation, capture, refund, settlement — need to reach the merchant's ERP. For Nordic merchants on Fortnox, Visma, Business Central, or similar systems, Junipeer handles the middleware layer, mapping Kustom's payment data to the ERP's expected format.

Settlement reconciliation is particularly important with Kustom, since the checkout handles multiple payment methods (card, Klarna, Swish, bank transfer) with different settlement timelines. The ERP needs to know which method was used and when funds arrive.

When Kustom fits — and when to look elsewhere

Kustom is a strong choice for Nordic and European merchants who want a high-converting embedded checkout with broad payment method coverage and minimal frontend development. The pre-fill and address autocomplete features work well in markets where shoppers expect a fast, familiar checkout.

For merchants who need deep checkout customisation, headless architectures with full frontend control, or markets where Kustom's coverage is thin, other approaches may work better. Adyen provides a payment gateway model with global reach. Klarna (as a standalone payment method, separate from Kustom's checkout) can complement other providers. Briqpay orchestrates multiple providers for complex B2B scenarios.

Beyond the integration

Embedding Kustom is one deliverable. Surrounding it: platform selection, shipping integration design, promotional rule testing, QA across payment methods, ERP data flow mapping, and rollout planning. A checkout that converts well in testing needs to be verified against real traffic patterns, edge cases, and the full return/refund cycle before it is production-ready.