Finding your OS

To get the latest enhancements and security updates, you should use the latest version of OS X. You can install updates you can install updates from the Mac App Store, from Software Update, or from the Apple Support website. To find build numbers for the version of OS X that came with your computer, refer to OS X versions (builds) for computers.

Finding the build number

To find the build number of the version of OS X you have installed, use these steps:

  1. From the Apple () menu, choose About This Mac.
  2. Click the Version number underneath where the window says “OS X”. The About This Mac window then displays your OS X version number in place of the version number.

About this Mac window

In the above example, OS X Mavericks is installed. You can also view your build number from the System Information or System Profiler app.

The build number depends on the version of OS X that is installed. When you install an OS X system software update or upgrade, you get a new build number. The build number of OS X included with a Mac may be different than what appears below.

OS X Mavericks

OS X Mavericks v10.9.2 Build 13C64
OS X Mavericks v10.9.1 Build 13B42
OS X Mavericks v10.9 Build 13A603

OS X Mountain Lion and Lion

OS X Mountain Lion v10.8.5 Build 12F37, 12F45 or 12F2029 (see notes)
OS X Mountain Lion v10.8.5 Build 12F37
OS X Mountain Lion v10.8.4 Build 12E55
OS X Mountain Lion v10.8.3 Build 12D78
OS X Mountain Lion v10.8.2 Build 12C54, 12C60, or 12C2034 (see notes)
OS X Mountain Lion v10.8.1 Build 12B19
OS X Mountain Lion Build 12A269
OS X Lion v10.7.5 Build 11G56 or 11G63 (see notes)
OS X Lion v10.7 Build 11A511


  • Build 12F2029 is available for the iMac (21.5-inch, Late 2013) with NVIDIA GeForce GT 750M only.
  • If you have Mountain Lion v10.8.5 (build 12F37), the OS X v10.8.5 Supplemental Update can be installed to get OS X v10.8.5 (build 12F45).
  • If you have Mountain Lion v10.8.2 (build 12C54), the OS X v10.8.2 Supplemental Update 1.0 can be installed to get OS X v10.8.2 (build 12C60).
  • Build 12C2034 is available for certain Macs only; it is installed by the OS X 10.8.2 Update (13″ MacBook Pro with Retina Display, 21.5″ iMac (Late 2012), and Mac mini (Late 2012).
  • If you have OS X Lion v10.7.5 (build 11G56), the Mac OS X v10.7.5 Supplemental Update can be installed to get OS X v10.7.5 (build 11G63).

OS X Snow Leopard and earlier builds

Mac OS X v10.6.8 Build 10K540 or 10K549
Mac OS X v10.5.8 Build 9L30, or 9L34 for Server 10.5.8 v1.1
Mac OS X v10.4.11 Build 8S165
Mac OS X v10.4 Tiger installation disc Build 8A428
Mac OS X v10.3.9 Build 7W98
Mac OS X v10.3.2 installation disc Build 7D28
Mac OS X v10.3 Panther installation disc Build 7B85
Mac OS X v10.2.8 Build 6R65 or 6R73
Mac OS X v10.2.3 installation disc Build 6G37, 6G35 for Server
Mac OS X v10.2 Jaguar installation disc Build 6C115
Mac OS X v10.1.5 Build 5S60 (5S66 with Networking Update 1.0)
Mac OS X v10.1 Puma installation disc Build 5G64 (5L14 or 5L17b with Security Update 10-19-01)
Mac OS X v10.0 Cheetah installation disc Build 4K78

Retail installation disc build numbers

Mac OS X v10.6.3 Install DVD Build 10D575
Mac OS X v10.6 Snow Leopard Install DVD Build 10A432, build 10A433 for Server
Mac OS X v10.5.6 Install DVD Build 9G66
Mac OS X v10.5 Leopard Install DVD Build 9A581