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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.Meta33Google27OpenAI15Anthropic5Parallel4Ahrefs2Apple1Perplexity1Yandex1First collected Sep 18, 2026Recent requestsAhrefsOct 30, 2026OpenAIOct 28, 2026Meta · unverifiedOct 12, 2026AhrefsOct 9, 2026Meta · unverifiedOct 9, 2026OpenAIOct 6, 2026GoogleOct 6, 2026Meta · unverifiedOct 4, 2026Meta · unverifiedOct 4, 2026Meta · unverifiedOct 3, 2026Meta · unverifiedOct 3, 2026Meta · unverifiedOct 3, 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.

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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 Nov 10, 2026 · Evidence page
  2. officialNetworks — ethereum.org · accessed Nov 10, 2026 · Evidence page
  3. officialHolesky and Hoodi Testnet Updates — Ethereum Foundation Blog · accessed Nov 11, 2026 · Evidence page
  4. officialPectra Mainnet Announcement — Ethereum Foundation Blog · accessed Nov 10, 2026 · Evidence page
  5. officialHolešky Testnet Shutdown Announcement — Ethereum Foundation Blog · accessed Nov 11, 2026 · Evidence page
  6. officialSolana Clusters — Solana Foundation · accessed Oct 31, 2026 · Evidence page
  7. officialUsing a test network — Bitcoin Core Onboarding · accessed Nov 11, 2026 · Evidence page
  8. officialGenesis block — Bitcoin Wiki · accessed Nov 11, 2026 · Evidence page
  9. newsEthereum Launches Long-Awaited Decentralized App Network — CoinDesk · accessed Oct 31, 2026 · Evidence page
  10. officialEIP-155: Simple replay attack protection — Ethereum Improvement Proposals · accessed Nov 11, 2026 · Evidence page
  11. officialThe Merge — ethereum.org · accessed Nov 10, 2026 · Evidence page
  12. officialTaproot — Bitcoin Optech · accessed Nov 11, 2026 · Evidence page