STRK20 PRIVATE SPRINT

Stealth Checkout

The accepting side of private payments on Starknet. STRK20 gives wallets a way to send money privately; this gives applications a way to get paid that way: an embeddable widget, per-invoice addresses, receipts, and a headless watcher that confirms payments over public RPC with no proving service in the loop.

Try it

Stealth Arcade →

A coin-op arcade that sells credits through the widget. Runs on a mock wallet, so the whole flow works with nothing installed.

NO WALLET NEEDED

Hosted invoice page →

Create a shareable payment link, or open one and pay it with a real wallet on Starknet mainnet.

MAINNET · NEEDS READY X

Merchant dashboard →

Create invoices, watch them settle, export the ledger. Talks to the watcher, the bundled confirmation server, and falls back to sample rows when it cannot reach one.

NEEDS THE WATCHER

Embed it

Not on npm yet: publishing is pending. Until then, clone the repo and npm install ./packages/strk20-pay.

import { mountCheckout, WalletApiAdapter } from "strk20-pay";

mountCheckout(document.getElementById("checkout")!, {
  invoice: {
    id: "order_1042",
    token: "STRK",
    amount: "25",
    mode: "address",
    receiveAddress: "0x…",   // fresh, one per invoice
    network: "mainnet",
    createdAt: Date.now(),
  },
  wallet: new WalletApiAdapter({ network: "mainnet", rpcUrl: "https://rpc.starknet.lava.build" }),
  // Must resolve to a BOOLEAN meaning "the money arrived". `r.ok` is only
  // "the server answered", and an unpaid invoice answers 200 too.
  confirm: (invoice) => fetch(`/api/paid/${invoice.id}`).then((r) => r.json()).then((b) => b.paid === true),
  onPaid: (receipt) => console.log(receipt),
});

What it does that nothing else here does

Confirms without proving. Each invoice gets its own receive address, and a payment is the sum of transfers into it since it was registered, never the balance sitting there. Public JSON-RPC is the only dependency.
Says what a payment reveals, before it is signed. The honesty panel is open by default and lists what goes on-chain and what does not. Overclaiming privacy is the one thing this must never do.
Shows the pool's fee, and gets its direction right. The STRK20 pool charges a flat 6 STRK per operation, which the docs do not cover yet. It comes out of a deposit and on top of a payment, so a payer who has to shield first pays it twice: 22 STRK to settle a 10 STRK invoice. The widget reads it from the contract, quotes the real total before you sign, and warns when it is larger than the invoice.
Never confirms money it did not see arrive. Partial payments become underpaid rather than expired, late ones become paid_late instead of being dropped, and an address is never released for reuse once anything has landed on it.
Signed webhooks that survive a restart. HMAC over timestamp.body, one delivery id per event to dedupe on, a retry queue persisted with the ledger, and a redelivery endpoint.

What it deliberately does not do

Execute refunds. It surfaces overpayments and shortfalls; moving money back is the merchant's, because a refund to a shielded payer has no address to go to.
Confirm note-mode payments headlessly. Note discovery is not available on mainnet, so that mode is confirmed wallet-side and labelled as such.
Price in fiat, bill on a schedule, or hold keys.