Express Checkout

Wallet and buy-now-pay-later flows, where the buyer authorizes payment in the provider’s own widget and Firmly confirms the result. Pick the provider you’re integrating — each provider page carries the shared setup and error handling for its sequence.

• Google Pay — single call; the wallet ceremony is client-side
• Klarna — start → authorize → complete order
• PayPal — start → authorize → complete order

Availability is per merchant. Check the cart’s payment_method_options before offering any of them; a provider the merchant has not enabled returns 404 GatewayNotFound.