Developer guide
Choose your checkout experience
Hosted method selector, selected-method checkout, or direct integration.
Choose where your buyer selects and completes the payment. All three experiences use the same methods, order identifiers and payment status contract.
These guides use the existing API. Direct integration keeps Key2Pay-Version: 2026-05-01 (also the default when omitted): HTTP 200, transactionId and payment instructions or paymentFormUrl. Opting into 2026-10-12 returns HTTP 201 awaiting_consent and checkoutUrl first. Hosted checkouts always collect buyer acceptance. Keep your current version and handle its response; a retry keeps the original contract.