Citrea is a rollup that utilizes Bitcoin's blockspace enhanced by zero-knowledge technology, enabling the development of applications directly on Bitcoin without altering its consensus rules. It introduces a Type 2 zkEVM, processing transactions in batches with succinct zero-knowledge proofs for easy verification. These proofs are inscribed in Bitcoin, optimistically verified via BitVM, ensuring data availability and permissionless access. Additionally, Citrea supports lightweight nodes through STARKs, facilitating easy blockchain verification. It also establishes a trust-minimized two-way peg with Bitcoin, using $BTC as its native token, referred to as $cBTC within Citrea.