Guess an ABI from an Ethereum contract address, even if it's unverified.

We parse EVM bytecode to find 4-byte JUMPI instructions and confirm that they're valid internal JUMPDEST targets.

By getting the 4-byte function signature hash selectors, we can use them to call functions on unverified contracts that were compiled using bytecode layout techniques similar to Solidity.

We can also look up the 4-byte selectors on APIs like 4byte.directory to discover possible original function signatures.

import { getDefaultProvider } from "ethers";
import { selectorsFromBytecode } from "@shazow/whatsabi";


const address = "0x7a250d5630b4cf539739df2c5dacb4c659f2488d"; // Or your fav contract address
const code = await getDefaultProvider().getCode(address); // Load the bytecode

const selectors = selectorsFromBytecode(code); // Get the callable selectors
console.log(selectors); // ["0x02751cec", "0x054d50d4", "0x18cbafe5", ...]

• abi.w1nt3r.xyz - A frontend for whatsabi by @w1nt3r_eth

• This technique of parsing function selectors from the EVM bytecode only works if the bytecode layout is similar to how Solidity compiles it. It's possible to write assembly/bytecode that does not conform to this layout, which will fail to detect function selectors. Note that functions are not a native thing in the EVM, but rather it's an abstraction layer built on top of it by compilers.
• This library does not try to guess the function arguments, if any. That would be a cool addition in the future!

• ethers.js for doing at least half of the hard work, even including an EVM bytecode parser for some reason!
• @jacobdehart for the library name and logo that is totally a wasabi and not a green poop!

MIT