The core difference between using the OKX DEX API to swap and placing an order on a regular exchange is that on-chain swaps require approval first, then execution. Approval gives the DEX contract permission to spend your tokens. Once this step is on-chain, it cannot be reversed. The swap is the actual trade. Many people get stuck at the approval step, or confuse "transaction broadcast" with "confirmed on-chain."
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First, understand that approval and swap are two separate on-chain transactions
The OKX DEX API swap process has two steps:
Step 1: Approval (Approve). For ERC-20 tokens (Ethereum, BSC, Polygon, and other EVM chains), your wallet must first grant the OKX DEX router contract permission to spend that token. Call GET /api/v6/dex/aggregator/approve-transaction, passing in chainIndex, tokenContractAddress, and approveAmount. The returned data field is the approval transaction calldata that needs to be signed, and dexContractAddress is the target contract address that needs approval.
Approval itself is an on-chain transaction and requires gas. After confirmation, your wallet balance will not change, but the on-chain allowance record will be updated.
Step 2: Execute the swap. After approval is confirmed, call the swap endpoint to get transaction data, sign it, and broadcast it. This is when your tokens are actually exchanged for another token.
If you are selling a native token (ETH, BNB, MATIC, etc.), skip the approval step and execute the swap directly.
Approval amount: do not default to unlimited
The approveAmount parameter determines the approval amount. The official API requires you to pass the value in the smallest unit. For example, 1 USDT (6 decimal places) should be passed as 1000000.
Many frontends default to unlimited approval (2^256-1) to avoid the hassle of re-approving every time you swap. But unlimited approval means that if the DEX contract has a vulnerability or your private key is leaked, that contract can transfer all of that token from your wallet. For unfamiliar tokens or tokens you do not use often, a safer approach is to approve only the amount needed for this transaction.
After executing the swap, on-chain confirmation does not mean instant arrival
After broadcasting the transaction, you get a txHash. This means the transaction has been submitted to the blockchain network, but it has not yet been packed and confirmed by miners/validators.
The OKX DEX API provides several verification entry points:
Query broadcast order list: GET /api/v6/dex/post-transaction/orders, passing in the wallet address and chainIn dex, returns the order list for that address, including txStatus (1 pending, 2 success, 3 failed) and txHash.
Query transaction details by txHash: If you are using X Layer or another chain, you can query the execution status of that transaction (success / fail / pending), gas consumption, and token transfer details by transaction hash.
Intent order status query (if using Intent Swap): GET /api/v6/dex/aggregator/intent/order-status, passing in orderUid, returns status codes: 0 in progress, 1 filled, 3 active, 5 auctioning, -1 failed, -7 expired, etc.
Verification standard: Only when the on-chain status becomes success or the intent order status becomes 1 (filled) is the swap considered complete. txStatus "pending" or status code "in progress" only means the transaction has been broadcast and the result is not yet determined.
Common failure reasons and troubleshooting order
If the swap fails or is not confirmed for a long time, check in this order:
Insufficient approval: If you approved 100 USDT but try to sell 200 USDT, the transaction will fail. Check whether approveAmount covers the amount of this swap.
Insufficient gas: Gas can spike when the network is congested. Insufficient reserved gas is a common cause of transaction failure. Check whether your wallet has enough native tokens (ETH, BNB, etc.) to pay for gas.
Slippage too low: During volatile market conditions, if the slippage tolerance is set too low and the price deviates beyond the range before execution, the transaction will fail. You can increase the slippage tolerance appropriately, but be aware that higher slippage may mean a worse actual execution price.
Insufficient liquidity: Some token pairs lack enough buy and sell orders to complete matching. Try a pair with higher trading volume, or retry at a different time.
Token risk interception: If the token contract is flagged as a risky address, the transaction will be blocked. In this case, you cannot force the transaction through the API and need to verify whether the token itself is trustworthy.
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References
- OKX Wallet·Approve Transactions, no update date indicated; checked on: 2026-10-02.
- OKX Wallet·Get Broadcast Order List, no update date indicated; checked on: 2026-10-02.
- OKX Wallet·Query Transaction Details by Hash, no update date indicated; checked on: 2026-10-02.
- OKX Wallet·Query Intent Order Status, no update date indicated; checked on: 2026-10-02.
- OKX·Reasons for Web3 Wallet DEX Transaction Failures and How to Resolve Them, published or updated on: 2025-07-28; checked on: 2026-10-02.
