pugixml is a lightweight, high-performance C++ XML processing library that provides a DOM-like interface, a fast non-validating parser, and XPath 1.0 support. It is designed for embedding into other applications and is used widely in game development, desktop applications, and embedded systems. The library is distributed as a single source file (`pugixml.cpp`) and header (`pugixml.hpp`), with optional header-only mode and extensive compile-time configuration via `pugiconfig.hpp`. It supports automatic encoding detection (UTF-8, UTF-16, UTF-32, Latin1), BOM handling, and full Unicode conversion. The architecture is monolithic but well-organized: the core parser uses recursive descent with custom memory pooling (page-based allocator) for fast DOM construction. The DOM tree is exposed through lightweight handle classes (`xml_node`, `xml_attribute`, `xml_text`) with iterator support for children and attributes. XPath queries are compiled into an internal representation and evaluated against the tree with full axis, function, and predicate support. Output is handled via an abstract `xml_writer` interface, allowing custom sinks. The library has zero external dependencies beyond the C++ standard library. Key entry points include `xml_document::load_file`, `load_buffer`, `load_string`, and `save_file`. Data flows involve loading XML from files, memory buffers, or streams into an in-memory DOM, then performing traversal, modification, or XPath queries, and finally saving the modified document. The library is used in production for parsing configuration files, serializing data, and processing XML messages in network protocols. It has an extensive test suite covering parsing edge cases, XPath compliance (W3C and Xalan), memory stress tests, and fuzzing harnesses. The codebase demonstrates strong craftsmanship: template-based parser specializations avoid runtime branching, memory management hooks allow custom allocators, and the compact mode reduces footprint for constrained environments. The library is well-maintained with active CI (GitHub Actions, AppVeyor), fuzz testing, and support for many compilers and platforms. The only notable technical drift is the continued support for legacy compilers (MSVC6, Borland), which adds preprocessor complexity but does not affect modern usage.