A simple bridge from dollars to your own wallet
pay-castle connects you to Coinbase's onramp. You stay in control of your wallet the entire time — we are only the front door.
Add your wallet
Paste your self-custodial wallet address, or connect a browser wallet (Coinbase Wallet, MetaMask, and other EIP-1193 wallets). We validate the address for the network you choose so funds can't go to a malformed address.
Pay with card or Apple Pay
Pick an amount and asset (USDC by default). When you continue, Coinbase's secure checkout opens. Coinbase verifies your identity if required and processes the card or Apple Pay payment. pay-castle never sees your card number.
Receive on-chain
After payment clears, Coinbase sends the crypto directly to the wallet address you provided — on Base, Polygon, or Ethereum. It's yours immediately and only you can move it.
What "non-custodial" means here
Custody is about who can move the money. With pay-castle, the answer is always you. We do not operate wallets on your behalf, we do not pool funds, and we never have the keys to your crypto. The flow is a direct line: your card → Coinbase → your wallet. pay-castle provides the interface and the secure server call that starts a Coinbase session; the funds themselves never pass through us.
Plain English: pay-castle is not a bank, exchange, or money transmitter. We don't hold your dollars or your crypto at any point. If pay-castle disappeared tomorrow, the crypto Coinbase already delivered would still be entirely in your wallet.
Fees
pay-castle adds nothing. Coinbase Onramp does not permit partner markups, and we don't add one. The only cost is Coinbase's own processing and network fee, which Coinbase displays to you inside its checkout before you confirm. You always see the exact crypto amount you'll receive and the fee before paying.
- Card / Apple Pay fee: set and shown by Coinbase at checkout.
- Network (gas) fee: varies by network; Base and Polygon are typically far cheaper than Ethereum mainnet.
- pay-castle fee: $0.00.
Supported assets & networks
At launch pay-castle defaults to USDC (a US-dollar stablecoin) delivered on Base for low fees, with Polygon and Ethereum also available. ETH and USDT are offered as additional assets. Coinbase's onramp supports many more assets and networks; we surface the options that are most useful for a first purchase.
Where it's available
Availability, supported payment methods, and limits are determined by Coinbase based on your location and applicable regulations. pay-castle is built for the United States (including New York) at launch. If Coinbase's onramp isn't available in your region or for your payment method, checkout will let you know.
Security
The CDP API secret that authorizes Coinbase sessions lives only on our server and is never exposed to your browser. Each purchase uses a fresh, single-use session token that expires in five minutes. Traffic is served over HTTPS, and our API is rate-limited and origin-locked.
That's the whole flow
Add a wallet, pay, receive. No custody, no markup, no surprises.
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