nDPI is a production-grade open-source deep packet inspection (DPI) library written in C, developed primarily by ntop.org. It identifies hundreds of network protocols by inspecting packet payloads using static signatures, heuristics, state machines, and machine learning classifiers. The library extracts rich metadata (TLS fingerprints, DNS queries, HTTP headers, etc.), computes flow risks (malware, DGA, obfuscation, anomalies), and supports output serialization in JSON, CSV, or TLV formats. It is designed to be embedded into network monitoring applications such as ntopng, nProbe, and Wireshark (via a Lua extcap plugin), and also ships as a standalone CLI tool (ndpiReader) and Python bindings. The codebase is well-structured with a modular dissector pattern, extensive fuzzing infrastructure, and a comprehensive test suite. While the primary focus is on library reuse, it also contains research-grade components like DGA detection models (scikit-learn/TensorFlow) and time-series anomaly detection, giving it a hybrid character leaning heavily toward a software library.