Arbitrum is designed to scale Ethereum, allowing transactions to be cheaper and faster. Its key feature is the ability to adjudicate and prove fraud on Layer 1, which is how it inherits Ethereum's security. Data fed into an Arbitrum Rollup chain is posted directly on Ethereum, providing visibility into Arbitrum activity. Validators move the Arbitrum chain state forward, and as long as there's one honest validator, the chain remains secure. If validators disagree, a dispute is narrowed down to a single computational step which is executed on Layer 1. Users typically have to wait 1 week to withdraw funds from Arbitrum to Ethereum, but fast-bridge applications can bypass this delay. Transactions are submitted on Layer 1 in batches, reducing transaction costs. Arbitrum was created with Ethereum compatibility as a top priority, meaning users can use Arbitrum with all their favorite Ethereum wallets and developers can build and deploy contracts with their favorite Ethereum libraries and tooling.