Using KuCoin Web3 Wallet

What Is a Swap and How Does It Work?

Last updated: 11/19/2025

1. What is crypto swap?

A crypto swap is the on-chain exchange of one cryptocurrency for another, executed by a smart contract instead of a centralized exchange (CEX). You trade directly from your self-custodial wallet, without depositing funds into an exchange account.

Typical examples:

  • Swapping ETH → USDT on the same chain

  • Swapping Token A → Token B through a DEX integrated into your wallet

KuCoin Web3 wallet also supports cross-chain swaps, where you swap tokens across two different networks using bridges or specialized protocols.

2. First-time swap vs. later swaps (Approval vs. Swap)

On most DEXs, a swap is logically one action, but technically it often happens in two on-chain transactions the first time you use a token:

2.1 Approval transaction (one-time per token & spender)

When you swap a token for the first time with a specific DEX (or contract):

  • You must approve that contract to spend your token.

  • This creates an on-chain permission (allowance) from your address to that smart contract.

  • The approval sets a limit (e.g. allow it to spend up to 1,000 USDT).

This is a separate transaction:

  • You sign it in your wallet.

  • You pay a gas fee.

  • The smart contract cannot move your tokens until this approval exists.

2.2 Swap transaction (for the actual trade)

Once approval is confirmed, you initiate the swap transaction:

  • The DEX contract checks your balance and allowance.

  • It transfers the specified amount of token from your wallet.

  • It executes the trade (via AMM pool, order book, or aggregator route).

  • It sends the output token back to your wallet.

You sign this second transaction and pay gas again.

This is the transaction that actually changes your token balances.

2.3 Future swaps with the same token & DEX

For later swaps using the same:

  • Wallet address

  • Token

  • DEX smart contract (spender)

You typically do not need another approval until:

  • You’ve already used up the approved amount, or

  • You revoke the approval, or

  • The DEX migrates to a new contract (new spender).

From a user perspective:

  • First time: you see Approve → then Swap.

  • Afterwards: often only Swap appears, because the token is already approved.

3. How to Swap in KuCoin Web3 Wallet

KuCoin Web3 Wallet provides a built-in swap interface within the KuCoin App. You can complete swaps directly from your wallet without leaving the app.

  1. Open KuCoin App

  2. Switch to Web3

  3. Navigate to Swap

At the bottom navigation bar, select Swap.

  1. Choose Tokens

  • Select the Pay token (the token you want to spend).

  • Select the Receive token (the token you want to receive).

  1. Enter Amount

Input how much of the Pay token you want to swap.

  1. Approve (if applicable)

  • If this is the first time your current wallet address is swapping this token inside KuCoin Web3 Wallet, you will need to complete an Approve transaction.

  • Approve the token, wait for on-chain confirmation.

  1. Confirm Swap

After approval (or if approval is already granted), tap Swap to submit your trade.

  1. Transaction Completion

Once the swap is processed on-chain, the received tokens will appear in your wallet.

  1. View Your Swap History

  • Go back to the Web3 home page

  • Tap More

  • Select History to view all transaction records, including approvals and swaps.

4. Common swap errors and what they mean

  • “Slippage / price impact too high” – The price moved or liquidity is too low; adjust slippage or reduce trade size.

  • “Insufficient allowance” – You need to re-approve the token with a higher amount.

  • “Insufficient balance / funds” – Not enough of the input token or not enough gas token (e.g. ETH) to pay fees.

  • Transaction pending for a long time – Network congestion or too low gas; you may need to speed up or cancel if supported.

5. Security tips for approvals & swaps

  • Only approve trusted contracts (use official links).

  • Avoid unlimited approvals for unknown protocols.

  • Periodically review and revoke old approvals using tools like explorers or approval-management dApps.

  • Double-check token contract addresses to avoid fake or scam tokens.

About KuCoin Web3 Wallet:
🔗 X (Twitter)
🔗 Telegram
🔗 Get KuCoin Web3 wallet