So I just ran a function from a contract on Ropsten from myetherwallet.com. It ran fine via metamask, but I was just wondering what chainID was in the rawTx file?


1 Answer 1


The chainid was added about 1 year ago in order to prevent replay attacks across channels. This was due to the ETH / ETC fork, but also applies to testnet and alternate chains (like Expanse). Here you can find a list of well known chainId values.

You can read about the discussion surrounding replay protection & EIP-155 here: https://github.com/ethereum/eips/issues/155

  • Awesome stuff to know. The sad part is that it doesn't explain why my transaction won't work, but that's a different question
    – thefett
    Commented Sep 5, 2017 at 17:38

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