5

I am trying to visualise transactions for Ethereum, currently, I know there are blockchain explorers such as Etherscan.io and Etherchain.org, however I don't want to keep calling their API to get data, rather use my own full node to get all the data I require since it give me greater control.

So I set up a full node and use the Web3JS library to get blocks and transactions. However, the Web3JS doesn't have the option to get an account via given address (unless I am mistaken). So, once I have the transaction object, I can figure out who the sender and receiver are, but I also want to know whether the sender or receiver is a contract or an account. I know on etherchain's API we can get accounts using the address, is it possible to do the same using geth and Web3Js?

Ethereum's yellow paper mentions that each account has a nonce, balance, storageHash and codeHash, so I thought it would be possible to get an account using addresses from the blockchain. Please help we figure out how to determine whether a given address is a contract or an account, without using blockchain explorers mentioned above?

Improve this question

1 Answer 1

Reset to default
5

No, it is not possible to determine from the address alone if it is a contract account or an externally owned account.

See this previous post on how contract addresses are generated:

Moreover it is expected that eventually all accounts will be contracts (this is called account abstraction):

You can use web3.js function web3.eth.getCode to get EVM bytecode associated with the address. It is assumed that for externally owned accounts it will return 0x0.

Improve this answer
3
  • Thanks, that was the notation I notice on etherchain, and was planning to do.
    – Athaheer
    Mar 2, 2017 at 9:47
  • While the concept of an externally owned account exists, it will always return 0x0 for web3.eth.getCode. (But 0x0 may also mean an account that just hasn't had a contract deployed to yet, so this comment is consistent with this answer. So depending on how strict you want to be, checking the return value of getCode could be a sufficient approximation.)
    – eth ♦
    Mar 2, 2017 at 15:36
  • The previous comment confuses me. If a contract hasn't been deployed yet at an address, then it is not a contract. In this sense, it seems to me that if getCode returns 0x0, then that address is clearly not a contract. Presumably, the OP is asking the question because he/she wants to know if an address that has interacted with his/her dapp is a contract (and perhaps behave differently). If it's already interacted, and getCode returns 0x0, isn't it true that it is not (and never will be) a contract? I'm not saying it is, I just confused by the previous comment.
    – Thomas Jay Rush
    Mar 12, 2017 at 16:28

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.