OnyX is a popular freeware utility for Mac OS X developed by French developer Joël Barrière that is compatible with both PowerPC and Intel processors. As a multifunctional tool for maintenance and optimization, it can control many basic Unix programs already built into OS X, including setting hidden preferences otherwise modified by using property list editors and the command line.


  • Verify the structure of the file system on the start-up volume
  • Repair disk permissions
  • Configure certain parameters hidden from the system and from certain applications
  • Empty System, User, Internet, Font caches
  • Force Empty the Trash
  • Rebuild Launch Services, CoreDuet database, XPC Cache...
  • Rebuild Spotlight and Mail indexes


Created in 2003 by Joël Barrière, a.k.a. Titanium, the program was originally meant to address its creator's personal needs. Developed using Xcode, Apple's software development environment (Cocoa + AppleScript Studio + Objective-C), OnyX is regularly updated by its author taking into consideration users' suggestions and requests. To do its job, the program uses OS X's standard Unix utilities, allowing their control through a graphical user interface without needing the command line. OnyX is freeware.


OnyX versions are specific to each version of Mac OS X and are not backward compatible. The program will not work correctly if used with an OS for which it was not designed.

The El Capitan (10.11) build is actively maintained. However, all previous versions in support of past operating systems are still available for download from the developer's website.

Version History

RedFormer official release
GreenCurrent official release
BlueCurrent test release