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RPC method

eth_chainId on Celo

Supported on SwiftNodes

Everything below was measured on 2026-10-13 by calling eth_chainId on Celo 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.

Celo 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 Celo a legacy transaction signed without a chain ID (pre-EIP-155). Its nodes refused it: "only replay-protected (EIP-155) transactions allowed over RPC". Sign with chain ID 42220; every mainstream library does this by default.

eth_chainId0xa4ec (42,220)
net_version42220

Example request

curl -s https://rpc.swiftnodes.io/rpc/celo?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 Celo before signing
import { createPublicClient, http } from "viem";

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

const id = await client.getChainId(); // 42220
if (id !== 42220) throw new Error(`wrong chain: ${id}`);

// Add Celo to a browser wallet
await window.ethereum.request({
  method: "wallet_addEthereumChain",
  params: [{
    chainId: "0xa4ec",
    chainName: "Celo",
    nativeCurrency: { name: "CELO", symbol: "CELO", decimals: 18 },
    rpcUrls: ["https://rpc.swiftnodes.io/rpc/celo?key=YOUR_API_KEY"],
  }],
});

Other methods on Celo

eth_chainId on other chains

Frequently asked questions

Does Celo support eth_chainId?

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

What is the Celo chain ID?

42220 in decimal, 0xa4ec in hex, as returned by eth_chainId on 2026-10-13.

How do I add Celo to MetaMask?

Call wallet_addEthereumChain with chainId 0xa4ec, the native currency CELO with 18 decimals, and your RPC URL; the example on this page has the full object.

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

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