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What is Ethereum mainnet chain ID?

Published Sep 18, 2026Updated Sep 19, 2026Last verified Sep 18, 2026Requests recorded in this site’s own server logs, with the crawler identity checked by reverse DNS or IP range.Google15Yandex1First collected Sep 18, 2026Recent requestsGoogleSep 20, 2026GoogleSep 20, 2026GoogleSep 19, 2026GoogleSep 19, 2026GoogleSep 19, 2026GoogleSep 19, 2026GoogleSep 19, 2026GoogleSep 19, 2026GoogleSep 19, 2026GoogleSep 19, 2026GoogleSep 19, 2026GoogleSep 19, 2026
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Quick answer

Ethereum mainnet uses chain ID 1. Chain IDs were introduced by EIP-155, created on 14 October 2016. The proposal builds a chain identifier into transaction signatures, so a transaction signed for one network cannot be replayed on another, such as Ethereum Classic or a testnet. Older Ethereum testnets had their own IDs, for example 3 for Ropsten and 5 for Goerli.

61 words12 sources

Answer

EIP-155 also lists 1337 as the default chain ID for Geth private chains [10]. Checking the chain ID in a wallet or tool is a practical way to confirm you are on mainnet.

Sources

  1. academicBlockchain Technology Overview (NISTIR 8202) — National Institute of Standards and Technology (via arXiv) · accessed Sep 19, 2026 · Evidence page
  2. officialNetworks — ethereum.org · accessed Sep 19, 2026 · Evidence page
  3. officialHolesky and Hoodi Testnet Updates — Ethereum Foundation Blog · accessed Sep 19, 2026 · Evidence page
  4. officialPectra Mainnet Announcement — Ethereum Foundation Blog · accessed Sep 19, 2026 · Evidence page
  5. officialHolešky Testnet Shutdown Announcement — Ethereum Foundation Blog · accessed Sep 19, 2026 · Evidence page
  6. officialSolana Clusters — Solana Foundation · accessed Sep 19, 2026 · Evidence page
  7. officialUsing a test network — Bitcoin Core Onboarding · accessed Sep 19, 2026 · Evidence page
  8. officialGenesis block — Bitcoin Wiki · accessed Sep 19, 2026 · Evidence page
  9. newsEthereum Launches Long-Awaited Decentralized App Network — CoinDesk · accessed Sep 19, 2026 · Evidence page
  10. officialEIP-155: Simple replay attack protection — Ethereum Improvement Proposals · accessed Sep 19, 2026 · Evidence page
  11. officialThe Merge — ethereum.org · accessed Sep 19, 2026 · Evidence page
  12. officialTaproot — Bitcoin Optech · accessed Sep 19, 2026 · Evidence page