This is a Go library for detecting the MIME type of files using magic number signatures. It implements a hierarchical detection tree rooted at 'application/octet-stream', allowing precise identification of over 200 file formats without any external dependencies. The library provides three detection entry points (byte slice, reader, file path) and supports concurrency via atomic and mutex locks. It includes custom parsers for CSV, JSON, OLE2/CDF, and MP3 frames, all optimized for performance and zero-copy where possible. The codebase is extensively tested with unit tests, fuzzing, and benchmarks, and is actively maintained with CI/CD, code scanning, and dependency automation. It is a standalone library with no runtime dependencies beyond the Go standard library.