What Is a Chain ID? EVM Network IDs Explained With a Table

By Step Exchange Research · October 22, 2026 · 2 min read

What Is a Chain ID? EVM Network IDs Explained With a Table

A chain ID is a number that identifies an EVM network: 1 for Ethereum, 56 for BNB Chain, 137 for Polygon, 8453 for Base, 42161 for Arbitrum One. Your wallet writes the chain ID into every transaction it signs, so a transaction meant for one network cannot be replayed on another. This protection comes from EIP-155 (2016). You need the chain ID when you add a network to a wallet manually.

Key Takeaways

  • Unique number per EVM network, included in every signed transaction.
  • Replay protection: a signature for chain 56 is invalid on chain 1.
  • Wallet check: MetaMask verifies the RPC returns the chain ID you entered.
  • Same address, different chains: the 0x address is the same; the chain ID tells which network.
NetworkChain IDHexGas token
Ethereum10x1ETH
Optimism100xaETH
BNB Chain560x38BNB
Gnosis1000x64xDAI
Polygon PoS1370x89POL
zkSync Era3240x144ETH
Base84530x2105ETH
Arbitrum One421610xa4b1ETH
Avalanche C-Chain431140xa86aAVAX
Linea591440xe708ETH
Scroll5343520x82750ETH

Sepolia testnet uses 11155111. Testnet tokens have no value; never buy them.

Chain ID vs Network ID

Ethereum nodes also have a network ID used for peer-to-peer connections. On most networks it equals the chain ID, but only the chain ID matters for wallets and signatures.

Where You Meet Chain IDs

  • Adding a network: wallets ask for name, RPC URL, chain ID, currency symbol and explorer. See how to add a network to MetaMask.
  • Wrong network prompts: a dApp asks you to “switch to chain 42161” when your wallet is on another network.
  • Bridges and aggregators: routes are defined by source and destination chain IDs; LI.FI-based widgets use them to show quotes.

Fake Networks

A malicious RPC can pretend to be a known network. Take RPC URLs and chain IDs from official docs or chainlist.org, and check that the explorer link is the network’s official one.

Related: gas tokens by chain, what is a layer 2.

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FAQ

What is a chain ID?

A unique number that identifies an EVM network, for example 1 for Ethereum, 56 for BNB Chain and 8453 for Base. Wallets include it in every signed transaction.

Why does the chain ID matter?

It stops a transaction signed for one network from being replayed on another (EIP-155), and wallets use it to check that an RPC endpoint really belongs to the network you selected.

Where do I find a network's chain ID?

In the network's official docs or on chainlist.org. MetaMask refuses to add a network if the chain ID does not match what the RPC reports.

Do Solana and Tron have chain IDs?

Not in the EVM sense. Non-EVM chains identify networks differently; bridge apps assign them their own internal IDs.

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