The Arbitrum One chain ID is 42161 (0xa4b1 in hex). Arbitrum One is an optimistic rollup on Ethereum developed by Offchain Labs. Gas is paid in ETH. Below are the exact settings MetaMask asks for, public RPC endpoints we tested on October 27, 2026, and a one-click button to add the network.
Arbitrum One Network Details for MetaMask
| Field | Value |
|---|---|
| Network name | Arbitrum One |
| RPC URL | https://arb1.arbitrum.io/rpc |
| Chain ID | 42161 |
| Currency symbol | ETH |
| Block explorer | https://arbiscan.io |
Copy these values exactly. If the RPC URL returns a different chain ID than the one you enter, MetaMask stops with a chain ID mismatch warning: that usually means a typo or an RPC for another network.
Arbitrum One RPC URLs (Tested October 27, 2026)
| RPC endpoint | Returned chain ID | Response time |
|---|---|---|
https://arb1.arbitrum.io/rpc | 42161 | 273 ms |
https://arbitrum-one-rpc.publicnode.com | 42161 | 183 ms |
https://arbitrum-one-rpc.blockreq.com/v1/rpc/public | 42161 | 189 ms |
We sent eth_chainId and eth_blockNumber to each endpoint from Europe on October 27, 2026; the table lists only endpoints that answered with chain ID 42161. The latest block was 518,769,878. Public endpoints are free and rate limited: for an app or a bot, use a paid provider or your own node.
How to Add Arbitrum One to MetaMask
- Click Add Arbitrum One to MetaMask above, or open MetaMask and go to Networks → Add a custom network.
- Enter the network name Arbitrum One, RPC URL
https://arb1.arbitrum.io/rpcand chain ID 42161. - Set the currency symbol to ETH and the block explorer to https://arbiscan.io.
- Save and switch to the new network. Your 0x address is the same as on other EVM networks.
Tip: Arbitrum Nova (chain ID 42170) is a separate network. Funds sent to your address on Nova will not show up on Arbitrum One, and the other way round.
Arbitrum Sepolia Testnet
| Field | Value |
|---|---|
| Network name | Arbitrum Sepolia |
| RPC URL | https://sepolia-rollup.arbitrum.io/rpc |
| Chain ID | 421614 (0x66eee) |
| Currency symbol | ETH |
| Block explorer | https://sepolia.arbiscan.io |
Testnet tokens come from faucets and are worth nothing. Do not send real ETH to a wallet connected to Arbitrum Sepolia.
How to Get ETH on Arbitrum One
The widget at the top of this page is set to swap into ETH on Arbitrum One: pick the token you have on another network, enter your address and sign once. Routes, fees and timing are covered in our Arbitrum One bridge guide.
Related
- What is a chain ID? - how chain IDs protect transactions
- How to add a network to MetaMask - the manual steps in detail
- Gas tokens by chain - what each network charges fees in
- All networks: chain ID list