EVM Chain ID List — Ethereum, Base, Arbitrum, Polygon & More

Every EVM network has a unique numeric chain ID that identifies it on-chain. This reference lists the canonical IDs for the major networks and explains how chainId feeds into EIP-155 replay protection.

Canonical EVM chain IDs

Ethereum Mainnet — 1. Optimism — 10. BNB Smart Chain — 56. Polygon — 137. Base — 8453. Arbitrum One — 42161. Avalanche C-Chain — 43114. Each ID is a stable integer registered for that network; wallets and clients use it to know which chain they are talking to.

chainId and EIP-155 replay protection

Before EIP-155, a transaction signed for one chain could be replayed on another chain that shared the same account and nonce. EIP-155 folds the chainId into the data that is signed, so a signature is only valid on the intended network. A transaction signed with chainId 1 cannot be replayed on chainId 137, and vice versa.

Where you encounter chainId

When constructing and signing a raw transaction you must set the chainId field so EIP-155 protection applies. eth_chainId returns the chain ID of the connected node as a hex quantity. Wallet UIs use it to switch networks and to warn when a dapp expects a different chain than the one selected.

chainId versus network ID

chainId is used for transaction signing and replay protection. The older network ID was used at the peer-to-peer layer for node discovery. On most networks the two values are identical, but they are conceptually distinct — always use chainId when signing.

Frequently asked

Is chainId the same as network ID?

Not conceptually. chainId is used for EIP-155 transaction signing and replay protection; network ID was used at the peer-to-peer layer. On most networks they share the same value, but you should use chainId when signing transactions.

Why do I need chainId when signing a transaction?

EIP-155 folds the chainId into the signed payload so the signature is only valid on the intended network. Without it, a signed transaction could be replayed on another EVM chain that shares your account and nonce.

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