Arc tooling

Connect MetaMask, ethers.js, viem, and web3.py to an Arc Mainnet or Arc Testnet node on Chainstack. Chain configuration, the USDC gas token, and the custom arc_* methods.

Arc is EVM-compatible, so the standard Ethereum libraries work against an Arc node without modification. The differences are in the chain configuration rather than in the code.

Chain configuration

Arc Mainnet and Arc Testnet differ only in the chain ID. Every other value below is the same on both networks.

Mainnet

Property	Value
Network	Arc Mainnet
Chain ID	5042
Native gas currency	USDC
Decimals	18
RPC URL	your Chainstack Arc endpoint
Multicall3	0xcA11bde05977b3631167028862bE2a173976CA11

Testnet

Property	Value
Network	Arc Testnet
Chain ID	5042002
Native gas currency	USDC
Decimals	18
RPC URL	your Chainstack Arc endpoint
Multicall3	0xcA11bde05977b3631167028862bE2a173976CA11

Arc pays gas in USDC, but the native currency carries 18 decimals, not the 6 that the USDC ERC-20 token uses. Balances are wei-denominated exactly as on Ethereum, so formatEther and from_wei(..., "ether") are the correct helpers. Treating the gas balance as 6-decimal USDC puts you out by a factor of 10¹².

See Arc methods for per-method availability and the API reference for interactive examples.

MetaMask

Add Arc as a custom network. On Chainstack, get your Arc endpoint, then in MetaMask select Add a custom network and fill in:

• Network name — Arc Mainnet or Arc Testnet
• Default RPC URL — your Chainstack Arc endpoint
• Chain ID — 5042 for mainnet, 5042002 for testnet
• Currency symbol — USDC

The block explorer field is optional in MetaMask. For Arc Mainnet, use explorer.arc.io. For Arc Testnet, use explorer.testnet.arc.io.

ethers.js

Install ethers.js:

Shell

npm install ethers

index.js

const { JsonRpcProvider, formatEther } = require("ethers");

const provider = new JsonRpcProvider("CHAINSTACK_NODE_URL");

async function main() {
  const network = await provider.getNetwork();
  console.log("Chain ID:", network.chainId.toString());

  const block = await provider.getBlockNumber();
  console.log("Block:", block);

  const balance = await provider.getBalance("0x19d7CF8eA0CE468417d1edA365a222a9dCBC7D27");
  console.log("Balance:", formatEther(balance), "USDC");
}

main();

Arc’s custom methods have no ethers helper, so call them with send:

index.js

const certificate = await provider.send("arc_getCertificate", [55000000]);
console.log("Round:", certificate.round, "signatures:", certificate.signatures.length);

viem

Arc is not in viem’s bundled chain list, so define it with defineChain:

Shell

npm install viem

index.mjs

import { createPublicClient, http, defineChain, formatEther } from "viem";

export const arcMainnet = defineChain({
  id: 5042,
  name: "Arc",
  nativeCurrency: { decimals: 18, name: "USDC", symbol: "USDC" },
  rpcUrls: { default: { http: ["CHAINSTACK_NODE_URL"] } },
  contracts: {
    multicall3: { address: "0xcA11bde05977b3631167028862bE2a173976CA11" },
  },
});

export const arcTestnet = defineChain({
  id: 5042002,
  name: "Arc Testnet",
  testnet: true,
  nativeCurrency: { decimals: 18, name: "USDC", symbol: "USDC" },
  rpcUrls: { default: { http: ["CHAINSTACK_NODE_URL"] } },
  contracts: {
    multicall3: { address: "0xcA11bde05977b3631167028862bE2a173976CA11" },
  },
});

const client = createPublicClient({ chain: arcMainnet, transport: http() });

console.log("Chain ID:", await client.getChainId());
console.log("Block:", await client.getBlockNumber());

const balance = await client.getBalance({
  address: "0x19d7CF8eA0CE468417d1edA365a222a9dCBC7D27",
});
console.log("Balance:", formatEther(balance), "USDC");

For the arc_* methods, use client.request:

index.mjs

const certificate = await client.request({
  method: "arc_getCertificate",
  params: [55000000],
});

web3.py

Install web3.py:

Shell

pip install web3

main.py

from web3 import Web3

web3 = Web3(Web3.HTTPProvider("CHAINSTACK_NODE_URL"))

print("Connected:", web3.is_connected())
print("Chain ID:", web3.eth.chain_id)
print("Block:", web3.eth.block_number)

address = Web3.to_checksum_address("0x19d7cf8ea0ce468417d1eda365a222a9dcbc7d27")
balance = web3.eth.get_balance(address)
print("Balance:", web3.from_wei(balance, "ether"), "USDC")

web3.py rejects lowercase addresses with InvalidAddress. Wrap any address you did not get from the library itself in Web3.to_checksum_address(), as above.

The arc_* methods are not in the web3.eth namespace, so send them through the provider:

main.py

version = web3.provider.make_request("arc_getVersion", [])["result"]
print("Node version:", version["git_version"])

certificate = web3.provider.make_request("arc_getCertificate", [55000000])["result"]
print("Round:", certificate["round"], "signatures:", len(certificate["signatures"]))

Two Arc behaviors that affect tooling

Only replay-protected transactions are accepted. Arc rejects pre-EIP-155 transactions on the RPC submission path with -32000 only replay-protected (EIP-155) transactions allowed over RPC. Every current library signs with the chain ID by default, so this only bites if you construct raw transactions by hand or use a very old signer.

Pending state is not readable. Subscribing to pending transactions fails, and eth_getBlockByNumber("pending") returns null rather than an error. Code that polls the pending block to estimate the next state will silently receive nothing. See What gives you mempool access.