Changelog

0.2.0 (2026-04-21)

Custom signatures

• Define your own MIME types via use MagicBytes.DefineSignatures and wire them in with config :magic_bytes, extra_signatures: MyModule
• defsignature/2 registers a prefix-based signature
• guards: true option generates guard macros on the custom module (e.g. MyModule.is_application_x_cld/1)
• Custom signatures are checked before built-ins; unmatched bytes fall through to built-in detection

Configuration

• config :magic_bytes, read_bytes: N — bytes read from input; defaults to 16, which satisfies all built-in signatures. Only needed if you define custom signatures whose prefix exceeds 16 bytes.
• config :magic_bytes, only: [...] — restrict detection to a specific set of MIME types; others return {:error, :unknown}
• config :magic_bytes, exclude: [...] — suppress specific MIME types

New built-in signatures

• image/jp2 (JPEG 2000)
• image/jxl (JPEG XL — bare codestream and ISO BMFF container)
• image/flif
• application/x-lz4
• application/vnd.apache.parquet
• application/vnd.apache.arrow.file
• application/vnd.android.dex

0.1.0 (2026-04-09)

Initial release.

• MagicBytes.from_path/1, from_binary/1, from_stream/1 for MIME detection
• Guard macros generated for all prefix-based signatures (is_image_jpeg/1, is_application_pdf/1, etc.)
• Support for 40+ MIME types across images, audio, video, documents, archives, executables, fonts, and databases