Mach-O

Mach-O, or Mach Object, is a form of OS X executable for the Mac platform. It has no characteristic file extension, and can be found extensionless or with .o, .dylib, or .bundle extensions, and can be used for standalone executables or linkable object or library files.

Format information

 * Format info in Apple's developer site

Metaformat files

 * Synalysis grammar file (for Hexinator / Synalize It!; more details)

Other links

 * Wikipedia article