The core idea of the unified USD order book is simple: when you see a BTC-USD trading pair, you don't need to hold fiat USD. USDC, USDG, and USD share the same order book. When placing an order, you choose "Pay with USDC," and the system automatically handles the conversion in the background. Pricing is displayed in USD, while settlement uses the stablecoin you selected. These two things are separate.
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Order Book and Pricing: Why It Shows XXX-USD
OKX displays all USD-priced trading pairs as XXX-USD, such as BTC-USD or ETH-USD. This naming doesn't mean you must trade with fiat US dollars. It is simply a unified way to show the pricing unit.
The benefit is that liquidity is merged. Previously, BTC/USDC and BTC/USD might have been two separate markets with fragmented depth. Now they share the same order book. If you trade with USDC and your counterparty trades with USD, you are both tapping into the same liquidity. The system handles the currency conversion in the background, so you don't need to manually swap coins first.
Settlement Currency: Trade with and Receive
There are two selectors on the order panel that determine which asset you actually use to complete the trade:
Trade with (payment currency): This is the asset you use to buy. If you hold USDC, select USDC, and your available balance will display correctly. If you choose the wrong one (for example, your account has USDC but you select USD), the balance will show 0, and the order will be rejected due to "insufficient margin."
Receive (receiving currency): This is what you receive after the trade is completed. When buying BTC, you can choose to receive BTC itself, or you can choose to receive a stablecoin-denominated value, depending on the specific product form.
If you and your counterparty select different currencies, OKX automatically handles the internal conversion. You don't need to do anything manually. Using USDC or USDG does not incur extra conversion fees. Maker/taker fees are charged according to your standard fee tier.
How to Use It
On the App or web platform, go to Spot Trading, select a USD trading pair (such as BTC-USD), open the Trade with selector on the order panel, choose the stablecoin you actually hold (USDC or USDG), confirm the Receive setting, and then place your order.
If you don't see these two selectors, update your App to the latest version first. Official documentation states that the App must be version 6.128.0 or above to use the unified USD order book.
Common Pitfalls to Avoid
A balance showing 0 doesn't always mean you have no funds. If your USDC is in your Funding Account, spot orders cannot use it. You need to transfer it to your Trading Account first. If you previously locked up that USDC in Earn or used it as margin, you need to redeem or release it first.
USD-M contract settlement currency is a separate setting. If you are trading USD-margined contracts with the XXX/USD UM suffix (perpetual or delivery), the settlement currency is selected separately under "Sub-account > Trading Settings > USD-M Settlement Currency". This is a different setting from the Trade with selector on the spot order panel, and the two do not affect each other. USD-M contract settlement supports USD, USDC, and USDG. The default is USD (in regions like the EEA, it may be USDC).
Withdrawals may be temporarily frozen. In some markets, withdrawals may be temporarily frozen for up to 10 days due to security reviews. If the withdrawal involves stablecoin redemption or fiat conversion, processing speed depends on the partner.
Is It Right for You?
If you already hold USDC or USDG and want to trade USD-priced spot pairs like BTC/ETH, the unified order book removes the step of "converting to USD first." You can place orders directly with stablecoins, and liquidity is the merged depth. This is suitable for users who don't want to make an extra currency conversion and already hold stablecoins on OKX.
If you insist on trading with fiat USD, it is also supported, but you need to deposit through the fiat channel first. For most crypto users, trading directly with USDC is the shorter path.
A leading global cryptocurrency platform,suitable for both beginners and experienced traders.
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References
- OKX·USD-margined futures contracts FAQ, page published or updated: 2026-09-01; verified: 2026-09-25.
- OKX·Unified USD Orderbook FAQ, page published or updated: 2025-07-03; verified: 2026-09-25.
- OKX·How do I trade a USD pair using USDC or another stablecoin?, page published or updated: 2026-09-02; verified: 2026-09-25.
- OKX·Unified USD Orderbook FAQ, page published or updated: 2025-07-03; verified: 2026-09-25.
- OKX·FAQ on USD-margined futures, page published or updated: 2025-10-12; verified: 2026-09-25.
