When using a smart contract, such as swapping a token, users usually need to approve that the smart contract is allowed to spend that token in their address. This is because non-native tokens, such as ERC-20 tokens, are smart contracts themselves, therefore they cannot be sent directly to a smart contract and call its functions.
Approve amount is the cumulative amount that a certain smart contract is allowed to spend a certain token of a certain address.
When using swap or bridge functions on "Market" page of ONTO, users can choose between two types of approve amount: suggested amount or unlimited amount.
- Suggested amount: the required amount of this transaction. This means that users need to approve again next time performing transactions of this token with this smart contract.
- Unlimited amount: the maximum amount of this data type, of which the effect is equivalent to unlimited. This means that users don't need to approve again in the future when performing transactions of this token with this smart contract, but are exposed with higher risk of token loss when there are hacks or bugs of this smart contract.
In general, the benefit of suggested amount is more secure, and the benefit of unlimited amount is more convenient and lower fees.