Convert Function to Function Selector

Generates the function selector (4 byte encoding) for a given function definition.

1. What is a function selector?

The function selector is a 4 byte identifier for functions in Solidity.

2. How is the function selector calculated?

The function selector is given by turning a function into a signature, hashing the signature with keccak256, and taking the first 4 bytes. An example and function follows below on how to derive the function selector.

function toSelector(string memory signature) internal pure returns (bytes4) {
  return bytes4(keccak256(signature));
}

Reversing the operation from function selector to function is not as straight-forward. Instead, we suggest the reversal to use the Ethereum Signature Database.

3. Examples

• function balanceOf(address owner) → 0x70a08231
• balanceOf(address) → 0x70a08231
• batch((address,address,uint256,bytes)[]) → 0xc16ae7a4

References

• viem: toFunctionSelector
• Solidity by Example: Function Selector