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The Crumb App

The Crumb web app at crumb-sepia.vercel.app provides a full-featured payment interface for users and merchants.

Wallets​

Crumb uses Privy embedded wallets for secure key management. When you sign up with your email, Privy automatically creates an embedded Ethereum wallet — your private key is managed by Privy's infrastructure and never exposed to the browser.

  • Email login — Sign in with your email via Privy. No passwords to manage or remember.
  • Embedded wallet — Your wallet is created automatically on first login. Privy handles key storage, recovery, and signing securely.
  • Testnet faucet — Get 2.5 USDC from the built-in faucet to start testing immediately.
  • Deposit & withdraw — Move USDC between your on-chain wallet and Circle Gateway. Withdrawals support cross-chain bridging.

Payment handles​

Every user gets a payment handle like @alice. Anyone can send USDC to your handle — no wallet address needed.

  • Visit crumb-sepia.vercel.app/@alice to send a payment
  • Scan a QR code to pay
  • Handles resolve to wallet addresses automatically

P2P transfers​

Send USDC to any handle or address. Transfers are:

  • Gasless — Signed off-chain via EIP-712, settled through Circle Gateway
  • Instant — No block confirmations to wait for
  • Push notifications — Both sender and recipient get notified

QR payments​

The app generates a QR code for your payment handle. Scan it with the built-in QR scanner to initiate a payment. The scanner recognizes:

  • Merchant payment URLs (crumb-sepia.vercel.app/pay/pay_abc123)
  • User handle URLs (crumb-sepia.vercel.app/@alice)
  • Plain handles (@alice)

Merchant features​

See the Merchant Setup guide for full details on:

  • Registering as a merchant
  • Creating payment links
  • Receiving webhooks
  • Managing your dashboard
  • Listing on the marketplace