Payments you can verify.

A contract-first API for invoices, hosted checkout and chain observations — with every state legible, traceable and yours to reconcile. Sandbox first; production stays switched off until it is earned.

Start the quickstart API reference Security model

What you can build today

Payment intents

Create an intent in EUR, USD, BRL or GBP, hand the customer a hosted checkout URL, and receive a signed webhook when the expected amount is final on-chain.

Honest sandbox

Bitcoin Testnet4 and Ethereum Sepolia activity comes from a deterministic simulator. Simulate exact, short, excess, late, reorganised and split payments on demand.

Signed webhooks

HMAC-SHA256 over the raw body with a timestamp, retries with backoff, dead-letter visibility and one-click replay. Verify in TypeScript, Go or Python.

Typed SDKs

@gryphem-pay/sdk, @gryphem-pay/react, @gryphem-pay/webhooks, gryphem_pay for Python and a Go module — all generated from or tested against the same OpenAPI 3.1 contract.

Ten minutes to a confirmed sandbox payment

Create an account in the dashboard and copy a test API key (gp_test_…).
POST /v1/payment-intents with an amount, a currency and your store id.
Open the returned checkout_url, pick a network and press Simulate payment.
Watch the intent move awaiting_payment → detected → confirming → confirmed and receive payment.confirmed.

QuickstartThe full walkthrough with curl, TypeScript, Go and Python.

Verify webhook signaturesThe exact algorithm and drop-in verifiers.

State machineWhat every status means and what you should do.

Regulatory statusWhat is not available, and why.