bytes4 is a commonly needed data type in Solidity, due to its use in msg.sig and, more broadly speaking, in function selectors (e.g. Contract.func.selector).

How can one convert bytes4 to bytes memory?

  • can we just use direct conversion bytes memory convertedData = new bytes256(msg.sig)?
    – Gleichmut
    Feb 13 at 10:33
  • 1
    bytes256 doesn't exist as a type. But, assuming you meant bytes32, no, you can't do that. Feb 13 at 10:57

2 Answers 2


abi.encodeWithSelector can be used for this:

bytes memory a = abi.encodeWithSelector(msg.sig);
bytes memory b = abi.encodeWithSelector(Contract.func.selector);

You can do it directly using abi.encode() or abi.encodePacked().

function get(bytes4 _val) public pure returns(bytes memory) {
        return abi.encode(_val);


Input: 0x60c06040

Output: 0x60c0604000000000000000000000000000000000000000000000000000000000

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