“Approve” isn’t another word for “transfer.”

Transaction data can describe a permission, an amount or a token ID. Context changes what the same bytes mean.

A wallet’s data field often begins with an eight-character hexadecimal selector after 0x. In the standard Solidity ABI, those four bytes identify a candidate function. Arguments follow in encoded words. Reading them can help you compare a proposed action with your intent, but it cannot replace checking the called contract.

1. A transfer names a recipient and a value

The common ERC-20 signature transfer(address,uint256) has selector 0xa9059cbb. Its first argument is a recipient address; its second is a raw integer amount. A value of 1,000,000 represents one token only if that exact token uses six decimal places. CallLens does not fetch or guess decimals.

2. An approval can grant spending permission

Under ERC-20, approve(address,uint256) identifies a spender and the allowance to set. It does not describe a token transfer to that spender. The maximum unsigned 256-bit integer is often used as a practically unlimited allowance. CallLens highlights that exact value under the ERC-20 interpretation without claiming to know the contract’s behavior.

3. NFTs reuse some of the same signatures

ERC-721 also defines approve(address,uint256). Here the integer is a token ID, not an allowance. The two standards also share transferFrom(address,address,uint256). The selector and encoded words alone cannot distinguish these meanings. Keep the interpretation set to “Unknown” until the token standard is independently established.

4. Collection approval is broader than one token

setApprovalForAll(address,bool) is used by ERC-721 and ERC-1155. Under those standards, true enables the operator for all of the owner’s tokens in the called collection or contract. false requests disabling that operator. Decoding either value does not mean a permission has actually changed.

A readable result is not a safety verdict. Four-byte selectors can collide, contracts can implement unexpected behavior, and a data field omits context such as the destination contract, network and native-currency value. CallLens does not simulate transactions, check balances or connect to your wallet.

Try it without sharing your data

Use the built-in fictional examples, or paste the full input-data field from an EVM wallet or explorer. Never paste a private key or recovery phrase. Processing is local; an offline HTML download is also available.

Open CallLens →