Keep Liquidity Always Permissionless.

A non-custodial API for accepting and distributing on-chain crypto payments.

Klappay funds never pass through Klappay. Every charge gets a predicted, immutable on-chain address — a 0xSplits split contract with recipients frozen at creation — and payments settle directly from payer to merchant on-chain. Our own operator wallet only ever pays the gas to trigger an already-deployed, already-immutable split; it can't redirect funds.

• Core API — charges, webhooks, real-time payment status over Server-Sent Events, and a full sandbox for testing without real transactions. USDC and USDT across seven networks: Base, Arbitrum, Optimism, Polygon, Ethereum, Avalanche, and BNB Chain.
• @klappay/types — TypeScript types and Zod schemas for the API's full request/response surface. MIT-licensed, framework-agnostic, zero networking.
• Official SDKs and a CLI — client libraries for integrating without hand-rolling HTTP calls and webhook signature verification, and a terminal client for creating charges, simulating sandbox events, and forwarding webhooks straight to localhost.

1. Create a charge. Klappay predicts (doesn't deploy yet) an immutable split contract address via CREATE2 — the same address regardless of which accepted token/network pair the payer ends up using.
2. Payer sends funds. USDC or USDT, on any network the charge accepts, straight to that address — no custody, no intermediate wallet.
3. Klappay detects and settles. The transfer is picked up in real time (webhook-driven, with a reconciliation fallback), and the split contract distributes the funds on-chain: merchant and platform fee, in one transaction.

• Webhooks — a full event vocabulary across payments, account, webhook-delivery, and security categories, HMAC-signed and retried on failure.
• Real-time (SSE) — stream a charge's status live instead of polling.
• Sandbox — simulate any charge or account event with a test API key, no real transactions required.
• Multi-organization accounts — a user can belong to more than one organization, each with its own role and API keys.

Full API reference, integration guides, and package docs live alongside each package's own repository.

_{Klappay is closed-source at its core — the API implementation isn't public — but the packages that make integrating against it easier (@klappay/types, the official SDKs, and the CLI) are.}