Arbitrum
An Ethereum layer-2 rollup. EVM-compatible with much lower fees than Ethereum mainnet, but a separate network.
Arbitrum is a layer-2 scaling network built on top of Ethereum using optimistic rollup technology. It is EVM-compatible and inherits Ethereum security, while offering much lower transaction fees and faster confirmations.
For a route screener, Arbitrum is a separate network even though it settles to Ethereum. USDT or USDC on Arbitrum is not the same on-chain balance as the same token on Ethereum mainnet, even though both use 0x addresses. Moving between them requires a bridge. When constructing an exchange route, make sure the network selector says Arbitrum on the side that holds the funds, otherwise the transfer can be sent to the wrong network and lost.