I know how to split but I'd like to know if, technically, all transactions on the Ethereum chain are automatically broadcasted on the "Ethereum Classic" chain and vice-versa or if replay "attacks" have to be specifically made by someone.

The one transaction I did to test it out, without using any splitter contract, was nearly instantly carried out on both chain. It was moreover valid on both chain, so the transaction happened on both chain (which was fine: it was just a test, with adresses I control).

So my question is: are all transactions automatically broadcasted to both chains and, for each chain, only those who are valid executed, or are there bots automatically replaying some (or all) the transactions?

  • BTW in case anyone wonder, I did the "split" by having someone who already split sent me some ETH on the ETH blockchain, so I had different amounts on both chains (1002 ETHs and 1000 ETCs). I then moved the total of 1002 ETHs which, obviously, couldn't be replayed on the ETC chain. I then proceeded to move the 1000 ETCs, which couldn't be replayed on the ETH chain (as my account there was already empty). Commented Jul 26, 2016 at 23:25
  • I'm not knowledgeable enough to answer this with certainty but wouldn't the two chains be completely different to each other both in terms of txs and current blocks. In your case you could mine on one chain and it would technically be rewarded to your account on both chains, which would be kind of disastrous for both chains I think.
    – mechanicum
    Commented Jul 27, 2016 at 6:11
  • 1
    Possible duplicate of How many transactions get automatically replayed on both sides of the fork?
    – Ethan
    Commented Jul 27, 2016 at 13:03

1 Answer 1


Transactions have to be explicitly relayed, it won't happen automatically, but apparently some people have set up bots to do this automatically so all transactions will get replayed.

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    I confirm that this is probably the case. I made two transactions of 1 eth on the forked chain and they were immediately cloned on the classic chain. i doubt people specifically aimed my accounts and care for 1 eth, so I think this is either a bot or a specific client version. But I admit that I don"t now the aim of replaying all the transactions. What I can't explain is why not all transactions are replayed. For instance, transactions that sent me eth from my mining pool were not replayed. That's a shame, why can't I also have free ETC ? :p Commented Jul 27, 2016 at 21:35

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