Currently, I am organizing a table for data on contracts by chain.

Can different chains have the same chain id?

I'd appreciate it if you let me know.

1 Answer 1


It is safe to assume different chains won't have same chain id.

In case two chains share same chain Id, transaction signed for one chain would execute on the other chain too, since they all have same execution layer.

Chain Ids are brought to prevent this from happening. So two chains shouldn't have same chain ID.

  • AFAIK, this was the case for Ethereum and Ethereum Classic for a while. Commented Dec 15, 2022 at 8:46
  • All transactions that happen on a chain can be replayed on another chain with the same ID. The difference is that the other chain will be useless because nobody will actually use it.
    – BonisTech
    Commented Mar 16, 2023 at 14:08

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