Lighter is a perpetual trading protocol that introduces a scalable, secure, transparent, non-custodial, and verifiable order book trading infrastructure within the Ethereum ecosystem. As an application-specific zk-rollup, it employs advanced cryptographic techniques and data structures. Lighter significantly improves the security and fairness of order book trading with its verifiable matching engine, ensuring scalable and efficient market price discovery. Thus, Lighter lays the groundwork for creating new, high-performance, and secure digital trading platforms.