filetype

filetype is a fast, dependency-free Go package for identifying binary file formats from their magic-number signatures. It examines file headers rather than relying on filename extensions, making detection useful for uploads and untrusted input. The API can match raw byte buffers and return a detected extension and MIME type. Developers can also check whether data belongs to supported categories such as images, audio, video, archives, or documents. Custom file-type matchers can be registered when an application needs formats outside the built-in set. The package is intentionally small and avoids external runtime dependencies. It is useful for validation, content routing, upload inspection, and lightweight file discovery in Go applications.