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RPC method

eth_chainId on Soneium

Supported on SwiftNodes

Everything below was measured on 2026-10-13 by calling eth_chainId on Soneium through the same endpoint customers use, and is re-measured weekly.

What eth_chainId does

Returns the chain ID (EIP-155) as a hex string. Wallets and libraries check it before signing, and the signature commits to it, so a transaction signed for one chain cannot be replayed on another.

Soneium chain ID, as measured

net_version returns the same number as decimal text. Older tools read net_version; use eth_chainId, which is the value signatures commit to.

We sent Soneium a legacy transaction signed without a chain ID (pre-EIP-155). Its nodes refused it: "invalid sender". Sign with chain ID 1868; every mainstream library does this by default.

eth_chainId0x74c (1,868)
net_version1868

Example request

curl -s https://rpc.swiftnodes.io/rpc/soneium?key=YOUR_API_KEY \
  -X POST -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","id":1,"method":"eth_chainId","params":[]}'
// Check you are on Soneium before signing
import { createPublicClient, http } from "viem";

const client = createPublicClient({
  transport: http("https://rpc.swiftnodes.io/rpc/soneium?key=YOUR_API_KEY"),
});

const id = await client.getChainId(); // 1868
if (id !== 1868) throw new Error(`wrong chain: ${id}`);

// Add Soneium to a browser wallet
await window.ethereum.request({
  method: "wallet_addEthereumChain",
  params: [{
    chainId: "0x74c",
    chainName: "Soneium",
    nativeCurrency: { name: "ETH", symbol: "ETH", decimals: 18 },
    rpcUrls: ["https://rpc.swiftnodes.io/rpc/soneium?key=YOUR_API_KEY"],
  }],
});

Other methods on Soneium

eth_chainId on other chains

Frequently asked questions

Does Soneium support eth_chainId?

Yes. eth_chainId answered on the SwiftNodes Soneium endpoint when our weekly probe called it through the customer path (2026-10-13).

What is the Soneium chain ID?

1868 in decimal, 0x74c in hex, as returned by eth_chainId on 2026-10-13.

How do I add Soneium to MetaMask?

Call wallet_addEthereumChain with chainId 0x74c, the native currency ETH with 18 decimals, and your RPC URL; the example on this page has the full object.

Soneium endpoints, live block height and WebSocket status are on the Soneium RPC page.

One key covers every chain we serve, and SwiftNodes has a free tier.