eth_chainId | Optimism

Optimism API method eth_chainId retrieves the current chain ID, which is a unique identifier for the blockchain network the node is connected to. The chain ID is crucial for transaction signing to prevent replay attacks across different chains.

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Parameters

• none — This method does not require any parameters.

Response

• result — the current chain ID, encoded as a hexadecimal string. For example, the chain ID for Optimism Mainnet is 0xa.

Use case

The eth_chainId method is essential for:

• Wallets and applications that sign transactions, as the chain ID is used as part of the signing process to ensure transactions are only valid on the intended chain.
• Applications that interact with multiple blockchain networks and need to confirm the network they are communicating with.

Try the eth_chainId RPC method yourself