Is there a way to extract ABI from a deployed contract?

Question

I am building a web UI for testing smart contracts and currently I have to supply the ABI for a contract I test. Is there a way to extract the ABI from a deployed contract (preferably programmatically)?

Answer 1

If the source code has been published to Etherscan, then they have an API to retrieve it. From https://etherscan.io/apis#contracts:

Get Contract ABI for Verified Contract Source Codes

https://api.etherscan.io/api?module=contract&action=getabi&address=0xBB9bc244D798123fDe783fCc1C72d3Bb8C189413&apikey=YourApiKeyToken

Answer 2

Go to EtherScan > enter the contract address > click on the Contract in the tab section heading > Scroll down to find the Contract ABI > click on the Copy icon to copy it

Answer 3

Yes, there are tools that try to recover ABI from bytecode.

For example porosity and mythril.

It is not always possible to recover ABI because bytecode does not contain function signatures but only last 4 bytes of function signature hash.

Answer 4

Deployed contracts are stored in bytecode so out of the box you can't extract the source ABI, however there are open source decompiling tools that attempt to recover the ABI.

What you can do is store the ABI JSON in IPFS and reference it by it's content hash.

Answer 5

You can also copy your ABI in Remix by going to Compile-->Details(ABI) section

Answer 6

Since you are developing the UI, I supposed you have developed the contract as well. In that case, if you are using Truffle, after deploying the contract you can find the ABI for each contract you deployed in the autogenerated build/contracts folder in your project, for example /build/contracts/Migrations.json.

Answer 7

If you are deploying by command line, you can read from the file where is previously builded, in the case of hardhat there is a example:

const fs = require("fs")
const path = require("path")

const getTheAbi = () => {
  try {
    const dir = path.resolve(
      __dirname,
      "./artifacts/contracts/HelloWorld.sol/HelloWorld.json"
    )
    const file = fs.readFileSync(dir, "utf8")
    const json = JSON.parse(file)
    const abi = json.abi
    console.log(`abi`, abi)

    return abi
  } catch (e) {
    console.log(`e`, e)
  }
}

Answer 8

When using React, you can check the ABI of deployed contracts by accessing the artifacts folder that is created after deployment:

artifacts -> contracts -> smartcontract.sol -> smartcontract.json