In 2026, the mantra "Not your keys, not your coins" has moved from cold storage into daily payments. Self-custodial cards represent a technical bridge between on-chain assets and the legacy Visa/Mastercard networks.
The Smart Contract Bridge
Unlike custodial cards where you deposit funds into an exchange's wallet, self-custodial cards like Solflare connect directly to your own wallet. When you swipe the card, a smart contract authorizes the liquidation of your assets in real-time.
Authorization vs. Custody
- Authorization: You grant the card network permission to pull a specific amount of assets only at the moment of a transaction.
- Custody: You retain the private keys to your wallet. The issuer cannot freeze your funds or use them for lending (Source: Public Smart Contract Audits).
Why Gas Fees Apply
Because these transactions occur on-chain (often on Layer 2s like Linea or Polygon), a small "Gas Fee" is typically required to process the payment. This is a cost unique to non-custodial spending that users should verify before choosing a card.