Arbitrum is an Optimistic Rollup that scales Ethereum, and consistently the largest L2 by total value locked. Its Nitro tech stack delivers low fees and high throughput while inheriting Ethereum's security through fraud proofs and on-chain data.
Arbitrum hosts one of the deepest DeFi ecosystems outside Ethereum mainnet — GMX, Aave, Uniswap, Pendle and many native protocols. The Arbitrum Orbit framework lets projects launch their own L3 chains that settle to Arbitrum, extending the ecosystem further.
ARB is the governance token of the Arbitrum DAO, which controls a large treasury and protocol parameters; ETH is used for gas. For users who want Ethereum-grade security with mainnet-class liquidity at a fraction of the cost, Arbitrum is a default destination.