Fintechs

Who it's for. Consumer-facing payment apps, neobanks, and B2C fintechs whose users either hold crypto and want to spend it as fiat, or hold fiat and want to fund a wallet. The defining characteristic is a user-facing app — your users, your UX, BRRR underneath.

Typical scenarios

• Crypto-to-card top-up. A user holds USDC in MetaMask. They tap "Top up card" in your app, sign one transaction, and EUR appears on their Holyheld card. (Deposit, SDK-driven.)
• Card-funded send. A user sends EUR from their Holyheld card to a friend's holytag — or to a wallet address — without leaving your app. (Withdraw or Deposit-to-holytag.)
• Operator-side settlement. Your fintech operates settlement for its own KYC'd customers, crediting their IBANs instead of a Holyheld card. (Multi-tenant Settlement.)

Recommended stack

Need	Reach for
End user signs in their browser wallet	SDK — wallet flows, EIP-2612 permits, cross-chain routing
End user already holds a Holyheld card and confirms in the Holyheld App	Card API — Deposit (offramp) and Withdraw (onramp) endpoints with 2FA
You settle on behalf of your own KYC'd customers	Multi-tenant Settlement API — customer registration, risk assessment, settlement to customer IBANs
Display token balances and prices in your UI	Web3 API — read-only blockchain helpers

Most consumer fintechs combine SDK + Card API: the SDK handles wallet-signing flows, the Card API handles card-balance state and SEPA transfers.

Architecture at a glance

   ┌────────────────────────┐
   │      Your fintech      │
   │   (web app, mobile)    │
   └──┬──────────────┬──────┘
      │              │
      ▼              ▼
  SDK in        Card API
  browser       (server)
  (Deposit /     │
   Withdraw)     │
      │          │
      ▼          ▼
   ┌────────────────────────┐
   │          BRRR          │
   │  routing · settlement  │
   └────────────┬───────────┘
                │
                ▼
   ┌────────────────────────┐
   │  Holyheld card balance │
   │  (or customer IBAN)    │
   └────────────────────────┘

The SDK and the Card API can ship side-by-side in the same product — the SDK for "user signs from a wallet", the Card API for "user already has a Holyheld card". Both settle EUR onto the same card balance.

Where to start

1. Quickstart — pick the SDK or the Card API based on where the user holds funds
2. Deposit — the most common flow on the platform
3. Supported Regions — confirm coverage for your target market

Where to next

• Deposit, Withdraw, Orchestrate — the three Core concepts hubs
• Card API section — endpoint inventory and 2FA flow
• Multi-tenant Settlement — operator-side settlement
• Webhooks — server-side notifications for terminal states