Comparing Arbitrum (ARB) and ZK-Rollup solutions from a technical perspective is essential to understand the different scaling approaches they bring to Ethereum. Both aim to solve Ethereum's scalability issues, but they rely on distinct technologies and mechanisms.

Arbitrum (ARB): Utilizes Optimistic Rollup technology. Optimistic Rollups process transactions off-chain and assume they are valid. A fraud-proof mechanism kicks in only if someone challenges a transaction. If a fraud is detected, the transaction is reverted.

ZK-Rollup: ZK-Rollups, on the other hand, use Zero-Knowledge Proofs to mathematically prove the validity of every batch of transactions. These proofs guarantee the correctness of transactions before they are posted to Ethereum’s main chain, offering instant finality.