{"id":735,"slug":"what-is-ethereum-mainnet-chain-id","question":"What is Ethereum mainnet chain ID?","intent":"informational","language":"en","url":"https://worldwiki.io/q/what-is-ethereum-mainnet-chain-id","entity":{"slug":"blockchain-mainnet","name":"Blockchain Mainnet","url":"https://worldwiki.io/entity/blockchain-mainnet"},"answer":{"short_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.","detailed_answer":"<p>EIP-155 also lists 1337 as the default chain ID for Geth private chains <span class=\"ref\">[10]</span>. Checking the chain ID in a wallet or tool is a practical way to confirm you are on mainnet.</p>","format":"paragraph","confidence":75,"verified_at":"2026-09-18 07:10:23","updated_at":"2026-09-18 16:10:23"},"sources":[{"id":171,"title":"Blockchain Technology Overview (NISTIR 8202)","url":"https://arxiv.org/abs/1906.11078","publisher":"National Institute of Standards and Technology (via arXiv)","type":"academic","accessed_at":"2026-09-18 18:01:27"},{"id":172,"title":"Networks","url":"https://ethereum.org/developers/docs/networks/","publisher":"ethereum.org","type":"official","accessed_at":"2026-09-18 18:01:28"},{"id":173,"title":"Holesky and Hoodi Testnet Updates","url":"https://blog.ethereum.org/2025/03/18/hoodi-holesky","publisher":"Ethereum Foundation Blog","type":"official","accessed_at":"2026-09-18 18:01:28"},{"id":174,"title":"Pectra Mainnet Announcement","url":"https://blog.ethereum.org/2025/04/23/pectra-mainnet","publisher":"Ethereum Foundation Blog","type":"official","accessed_at":"2026-09-18 18:01:29"},{"id":175,"title":"Holešky Testnet Shutdown Announcement","url":"https://blog.ethereum.org/2025/09/01/holesky-shutdown-announcement","publisher":"Ethereum Foundation Blog","type":"official","accessed_at":"2026-09-18 18:01:29"},{"id":176,"title":"Solana Clusters","url":"https://solana.com/docs/references/clusters","publisher":"Solana Foundation","type":"official","accessed_at":"2026-09-18 18:01:30"},{"id":177,"title":"Using a test network","url":"https://bitcoincore.academy/testnets.html","publisher":"Bitcoin Core Onboarding","type":"official","accessed_at":"2026-09-18 18:01:30"},{"id":178,"title":"Genesis block","url":"https://en.bitcoin.it/wiki/Genesis_block","publisher":"Bitcoin Wiki","type":"official","accessed_at":"2026-09-18 18:01:31"},{"id":179,"title":"Ethereum Launches Long-Awaited Decentralized App Network","url":"https://www.coindesk.com/markets/2015/07/30/ethereum-launches-long-awaited-decentralized-app-network","publisher":"CoinDesk","type":"news","accessed_at":"2026-09-18 18:01:33"},{"id":180,"title":"EIP-155: Simple replay attack protection","url":"https://eips.ethereum.org/EIPS/eip-155","publisher":"Ethereum Improvement Proposals","type":"official","accessed_at":"2026-09-18 18:01:33"},{"id":160,"title":"The Merge","url":"https://ethereum.org/roadmap/merge/","publisher":"ethereum.org","type":"official","accessed_at":"2026-09-18 18:01:18"},{"id":181,"title":"Taproot","url":"https://bitcoinops.org/en/topics/taproot/","publisher":"Bitcoin Optech","type":"official","accessed_at":"2026-09-18 18:01:33"}],"published_at":"2026-09-18 07:10:23"}