ChainsArbitrum: chain ID, RPC URLs and explorers

Arbitrum: chain ID, RPC URLs and explorers

The main Arbitrum RPC is https://arb1.arbitrum.io/rpc, run for Arbitrum One, the chain with ID 42161. Value locked in Arbitrum apps is $1.4 billion at this check, per DefiLlama.

By Onchain Wiki editors · checked November 9, 2026, 11:17 UTC

Arbitrum One network details, RPCs tested November 9, 2026
Chain ID	42161 (0xa4b1)
Native token	ETH
Public RPC	`https://arb1.arbitrum.io/rpc` `https://arbitrum-one-rpc.publicnode.com`
Explorer	arbiscan.io
USDT contract	`0xFd086bC7CD5C481DCC9C85ebE478A1C0b69FCbb9`
USDC contract	`0xaf88d065e77c8cC2239327C5EDb3A432268e5831`
Mainnet since	August 31, 2021
Official docs	docs.arbitrum.io/for-devs/dev-tools-and-resources/chain-info

Arbitrum Chain ID for One and Nova

The Arbitrum chain ID is 42161 for Arbitrum One and 42170 for Arbitrum Nova, a separate chain with its own settings. Both numbers match Arbitrum's chain info page and the chainid.network registry, and both chains pay gas in ETH.²

Arbitrum network settings from docs.arbitrum.io, read November 8, 2026
Field	Arbitrum One	Arbitrum Nova
Chain ID	42161	42170
Currency symbol	ETH	ETH
Official RPC	`https://arb1.arbitrum.io/rpc`	`https://nova.arbitrum.io/rpc`
Explorer	`https://arbiscan.io`	`https://arbitrum-nova.blockscout.com`

Arbitrum RPC Endpoints That Passed

Three Arbitrum RPC endpoints passed our eth_chainId test on November 8, 2026, answering 0xa4b1 for One and 0xa4ba for Nova.¹

https://arb1.arbitrum.io/rpc, Arbitrum One's official endpoint.
https://arbitrum-one-rpc.publicnode.com, a free Arbitrum One endpoint from PublicNode.³
https://nova.arbitrum.io/rpc, the official endpoint for Nova only.

Nova has thinner tool support than One. Arbitrum's docs say Nova Arbiscan, Alchemy and Tenderly all dropped Nova on January 31, 2026, which is why Blockscout is the Nova explorer above. For test ETH on the One side, use the Arbitrum Sepolia faucet.

Arbitrum One vs Arbitrum Nova

Arbitrum One and Arbitrum Nova differ in where they keep transaction data. One is an optimistic rollup: it posts all of its data to Ethereum and assumes batches are valid unless someone proves otherwise during a one-week dispute window.⁴ Nova uses AnyTrust, which hands data to a 7-member Data Availability Committee instead of posting all of it, trading an extra trust assumption for lower fees.

Offchain Labs opened Arbitrum One to the public on August 31, 2021⁵ and launched Nova on August 9, 2022.⁶ Offchain Labs still runs the Arbitrum One sequencer, the service that orders transactions. The layer 2 guide compares this design with other rollups.

USDT0 and USDC on Arbitrum

USDT0 and USDC on Arbitrum both have clear issuers, though only USDC comes from the company behind the dollar reserves. Circle issues native USDC at 0xaf88d065e77c8cC2239327C5EDb3A432268e5831.⁷ An older bridged USDC.e sits at 0xff970a61a04b1ca14834a43f5de4533ebddb5cc8; it is Ethereum USDC moved over the Arbitrum bridge, and Arbitrum's docs say it took the .e suffix after Circle arrived in 2023.⁸

Tether's supported protocols page has no Arbitrum entry, so the USDT on Arbitrum is not a Tether-listed contract.⁹ The token at 0xFd086bC7CD5C481DCC9C85ebE478A1C0b69FCbb9 was upgraded in 2025 to USDT0, a version minted against USDT locked on Ethereum and run by Everdawn Labs, per USDT0's deployment list and Cointelegraph's reporting.¹¹ DefiLlama counts $799 million of USDT on Arbitrum. The USDT networks page shows the other chains.

Questions People Ask About Arbitrum: chain ID, RPC URLs and explorers

These are the questions people ask next about Arbitrum: chain ID, RPC URLs and explorers.

What is the Arbitrum chain ID?

The Arbitrum chain ID is 42161 for Arbitrum One and 42170 for Arbitrum Nova. In hex those are 0xa4b1 and 0xa4ba. Arbitrum's docs and the chainid.network registry agree on both.

What is the Arbitrum One RPC URL?

The Arbitrum One RPC URL from Arbitrum's docs is https://arb1.arbitrum.io/rpc. It returned chain 42161 in our November 8, 2026 test, and so did PublicNode's free endpoint at arbitrum-one-rpc.publicnode.com.

What is the Arbitrum Nova RPC?

The Arbitrum Nova RPC is https://nova.arbitrum.io/rpc, and it serves chain ID 42170 only. Funds sent to a Nova address arrive on Nova, not on Arbitrum One, so match the network in your wallet before sending.

Is USDT on Arbitrum issued by Tether?

USDT on Arbitrum is not on Tether's list of supported contracts. The token there is USDT0, operated by Everdawn Labs and backed by USDT locked on Ethereum, at 0xFd086bC7CD5C481DCC9C85ebE478A1C0b69FCbb9.

Sources

Every number on this page comes from these sources, checked November 9, 2026.