Card checkout for your store, stablecoin in your own wallet.
Sardium adds a white-label checkout to your store. The shopper pays by card or a local payment method through a licensed payment provider, the stablecoin lands in the shopper's own wallet, and the shopper sends the payment to yours. We never hold the funds.
Selling online across borders comes with friction.
Card acceptance is hard to get
Opening a card acquiring account that takes buyers from many countries is slow for a small store, and the account arrives with the acquirer's rules attached.
Disputes long after delivery
A card payment can be disputed weeks after the order has shipped. The store answers for it, and the time spent gathering evidence is yours.
Payouts you wait for
Card revenue reaches you on the acquirer's schedule, sometimes with part of it held back. Your cash flow follows their rules, not yours.
Three steps. The funds never rest with us.
The buyer pays by card
The checkout sits in your site, with your brand. The buyer pays by card or a local payment method through a licensed payment provider, which handles the card and the identity checks (KYC).
The stablecoin goes to the buyer's own wallet
The provider delivers USDC or USDT to a self-custody wallet that belongs to the buyer. Only the buyer holds its keys.
The buyer pays you
The buyer signs the payment from that wallet and sends it to your self-custody wallet. Sardium never holds or touches the funds; it runs the checkout and sends you signed webhooks.
What your store gets
Your brand at checkout
The checkout carries your colour and your name, so it reads as part of your store.
Sales in your own wallet
Payments arrive as USDC or USDT in a self-custody wallet you control, on Polygon, Base, Arbitrum or Optimism.
Orders updated by signed webhook
Your store hears about each payment through signed webhooks, and every transfer can be checked on chain.
An iframe, not a rebuild
Add the checkout with your publishable key and wallet address. Full documentation comes with your access.
Questions, answered honestly.
Who holds the funds?
No one in the middle. The card payment is processed by a licensed payment provider, the stablecoin lands in the buyer's own self-custody wallet, and the buyer signs and sends the payment to your self-custody wallet. Sardium holds neither fiat nor crypto at any stage.
Does the buyer need a crypto wallet already?
No. The checkout gives the buyer a self-custody wallet of their own, and only the buyer holds its keys. The stablecoin arrives there first, and from there the buyer pays you.
What if the buyer disputes the card payment?
The card purchase is between the buyer and the licensed payment provider, and a dispute about it is handled there, under the provider's rules. What reaches you is a stablecoin transfer the buyer signed from their own wallet. A card network cannot reverse a transfer on chain, so a refund to the buyer is one you decide on and send. Consumer law where you sell still applies to you.
Can I refund an order?
Yes. The payment sits in your own wallet, so a refund is a transfer you send back to the buyer, under your own returns policy.
Who checks the buyer's identity?
The licensed payment provider, under its own licence. It may ask a buyer to verify before the first purchase, and it sets its own conditions, such as purchase limits. Card payment is available where the provider serves the buyer's country.
Which stablecoins and networks can I receive?
USDC and USDT on Polygon, Base, Arbitrum and Optimism.
What do I need to start?
A registered business, a self-custody wallet address on a supported network, and business verification (KYB) with us. Fill in the application form and we will guide you through it. Some lines of business cannot be served; the application page lists them.
Bring a crypto checkout to your store.
Fill in the application form; we will guide you through business verification (KYB).
Request access