eth_chainId on Arbitrum One
Returns the chain's EIP-155 chain ID as a hex string. Wallets and libraries call it to confirm they're talking to the expected network.
This is the EIP-155 id used for replay-protected signing — libraries check it on connect, and a mismatch is the usual cause of 'wrong network' errors. It's distinct from net_version (network id); prefer chainId in new code.
Arbitrum One endpoint (public — no key)
https://rpc.nodeflare.app/arb/publicMethod
eth_chainId
Cost
1 CU
Chain ID
42161
Block time
~250 ms
Finality
<1 s sequencer · L1-final ~13 min
Network on Arbitrum One
Chain ID 42161 (0xa4b1) — Arbitrum One. Arbitrum Nova (42170) is a separate AnyTrust chain with its own RPC; the two are not interchangeable.
Parameters
None.cURL
curl https://rpc.nodeflare.app/arb/public \
-X POST \
-H 'content-type: application/json' \
-d '{"jsonrpc":"2.0","method":"eth_chainId","params":[],"id":1}'ethers.js
import { ethers } from 'ethers';
const provider = new ethers.JsonRpcProvider(
'https://rpc.nodeflare.app/arb/public'
);
const result = await provider.send('eth_chainId', []);Try it live
Runs the example above against the public Arbitrum One endpoint — straight from your browser.
eth_chainId on Arbitrum One — FAQ
How do I call eth_chainId on Arbitrum One?
POST a JSON-RPC 2.0 request with "method": "eth_chainId" to NodeFlare's Arbitrum One endpoint at https://rpc.nodeflare.app/arb/public. No API key is required for the public endpoint.
What does eth_chainId cost on the free tier?
eth_chainId is weighted at 1 compute unit per call. The free tier includes 2,000,000 CU/month, so that is roughly 2,000,000 eth_chainId calls per month — no credit card.
Is eth_chainId available on the public Arbitrum One endpoint?
Yes. eth_chainId works on the public Arbitrum One endpoint (https://rpc.nodeflare.app/arb/public) with no API key, rate-limited per IP. A free key adds higher limits and a dedicated path.
Anything Arbitrum One-specific to know when using eth_chainId?
Chain ID 42161 (0xa4b1) — Arbitrum One. Arbitrum Nova (42170) is a separate AnyTrust chain with its own RPC; the two are not interchangeable.
Call eth_chainId on Arbitrum One with a free key
2,000,000 compute units/month, heavy methods unlocked, every chain included. No credit card.
Get your free API key →