What is Arbitrum?

Arbitrum is a Layer-2 rollup on Ethereum. In July 2026, David Hoffman noted that Ethereum gets 0.15% for data availability from rollups like Arbitrum. He also reported that on July 10, Robin Hood chain flipped Base in user operations per second, with 117 ops/sec vs 93 on Base. Ryan Sean Adams argued that a critical bug in Arbitrum should be treated as an Ethereum vulnerability, triggering an L1 fork. An unnamed speaker identified Base and Arbitrum as their real competition.