Cashu.space is the official site for Cashu, an open-source Chaumian ecash protocol built on Bitcoin and Lightning Network. It enables fast, private, and simple digital cash payments—like physical cash but for online/in-person use—via bearer tokens, blind signatures for privacy, and instant peer-to-peer transfers. Key features include web integration, developer tools (NUTs, libraries in Python/Rust/etc.), wallets/apps, and resources for building mints or payment systems.