Crow is a modern C++ microframework for building HTTP and WebSocket services. Designed as a single-header library (or modular headers), it provides a Flask-like routing system with typed URL parameters, a middleware pipeline (global and per-route), built-in JSON parsing and generation, Mustache templating, multipart form handling, static file serving, gzip/deflate compression, and SSL/TLS support. The framework is header-only and leverages C++17/20 features such as std::string_view, std::optional, and constexpr where possible. It includes a comprehensive test suite (Catch2), fuzz testing for security, and extensive documentation via MkDocs and Doxygen. Crow is packaged for multiple platforms (Vcpkg, Homebrew, AUR, Conan, Nixpkgs) and is used in production by several open-source projects. The architecture is event-driven, built on top of Asio (standalone or Boost), with a focus on performance and simplicity. Reusable components include a standalone JSON library, base64 utilities, and a flexible middleware system.