What a token approval does before a wallet trade

A token approval gives a smart contract permission to spend a specific token from your wallet. It is often a separate step before a swap because the contract needs that permission before it can move the tokens.

The approval is a permission to spend, not the trade itself.

Why does a wallet ask for approval before a trade?

Most tokens on Ethereum and compatible networks follow the ERC-20 standard, which keeps the tokens in your wallet until you authorize a contract to use them. A swap contract cannot take them just because you connected your wallet or selected a trade.

The wallet usually shows which token and spender contract the approval covers. A fuller walkthrough of the step appears in the paraswap article; the same permission model applies to token swaps more broadly.

Approval and swapping may require two wallet confirmations and two on-chain transactions. Some tokens and apps support signature-based permissions that can combine or change the approval step, but the wallet still needs your authorization.

What does the approval amount control?

The amount sets the maximum number of tokens the contract may spend under that permission. An exact approval limits access to the amount needed for the trade, while an unlimited approval lets the contract spend any amount of that token up to your balance.

• Exact amount: limits the permission, but a later trade may need another approval.
• Unlimited amount: can avoid repeat approvals for that contract, but leaves broader permission in place.
• Existing allowance: may cover a later trade, so the wallet might not ask for approval again.

Unlimited approvals are convenient, but they do not mean a contract can spend other tokens or exceed your wallet balance. For most people, an exact approval is the narrower choice; repeat approvals may cost extra time and transaction fees.

What does approval cost, and how can you remove it?

On networks that charge gas, approval is an on-chain transaction and costs a network fee. The fee depends on network conditions and the chain, and the swap itself may require a separate fee-paying transaction.

Before signing, check that the token, amount, network and spender match the trade you intended. A wallet or app can display the spender’s address; if the details do not match, reject the request and inspect the transaction in a trusted interface.

You can usually reduce an allowance or set it to zero through a wallet or an allowance-management tool. That change is another on-chain transaction and may cost gas; it stops future spending under that permission but does not undo a trade already completed.