From The Apple Wiki
< Firmware‎ | Mac

Releases of Mac OS X prior to Mavericks were paid upgrades. As such, full installers mostly do not exist for these versions. Apple made exceptions for Mac OS X Lion and OS X Mountain Lion, which were released as a free download on the Apple Support website on 2 July 2021. On 24 October 2019 and 10 February 2015, in preparation for an Apple Software Update certificate expiring causing installer packages to display an integrity error and refuse to install, Apple reissued many updates, signed with a new certificate.[1][2]

To install copies of macOS without updated certificates, change the Mac's system clock to sometime prior to 24 October 2019 before attempting installation, and reset it to the current date afterwards. If the Mac doesn't have an existing operating system installation, this may be done from the installation environment by clicking Utilities → Terminal, then entering date 1001000019 to set the date to midnight on 1 October 2019. Press ⌘Q to quit Terminal and return to the installer.

Most downloads are a patch updater (upgrading directly from the previous version), or combo updater (upgrading from any earlier version in the same major release). To perform a clean installation of macOS, use a full release build.

OS X Mountain Lion is the first release to move server components from a separate operating system release, to an OS X Server application installed on top of the operating system.

Version Build Release Date Download URL SHA1 Hash File Size Documentation Notes
10.8 12A269 25 July 2012 Paid Release
10.8.1 12B19 23 August 2012 OSXUpd10.8.1.dmg[dead link] ? ? Release Notes [Archived 2014-08-13 at the Wayback Machine]
10.8.2 12C54 19 September 2012 OSXUpd10.8.2.dmg[dead link]
Release Notes [Archived 2014-09-23 at the Wayback Machine]
Security Notes
12C60 4 October 2012 OSXUpd10.8.2Supp.dmg c81731a9c562eb06f86efbfb55e3cc9523ad9730 27,876,466 Release Notes [Archived 2014-09-23 at the Wayback Machine]
12C2034 23 October 2012 ? ? ?
12C3104 29 November 2012 OSX10.8.2SupplementalUpd2.0.dmg 75954a6493558fb468b27d2859f1437a2e17efde 1,197,722 Update reissued due to "Volume does not meet requirements for this update" error.
10.8.3 12D78 14 March 2013 OSXUpd10.8.3.dmg[dead link]
Release Notes [Archived 2014-10-10 at the Wayback Machine]
Security Notes
10.8.4 12E55 4 June 2013 OSXUpd10.8.4.dmg[dead link]
Release Notes [Archived 2014-08-29 at the Wayback Machine]
Security Notes
12E3067 10 June 2013 Initial release for MacBook Air (Mid 2013)
12E4022 25 September 2013 Initial release for iMac (21.5-inch, Late 2013) and iMac (27-inch, Late 2013)
10.8.5 12F37 12 September 2013 OSXUpd10.8.5.dmg[dead link]
Release Notes [Archived 2014-09-12 at the Wayback Machine]
Security Notes
12F42 24 September 2013 ? ? ? Release Notes [Archived 2014-09-12 at the Wayback Machine]
Security Notes
12F45 3 October 2013 OSXUpd10.8.5Supp.dmg 5b10d728f5043e7b056e24f30596fa34031d859d 19,662,726 Release Notes [Archived 2014-09-12 at the Wayback Machine]
Security Notes
2 July 2021 InstallMacOSX.dmg 4b9bc933f50abe824b93ba9eebd8f57f1609ccdb 4,720,237,409 DL2076 Free re-release of Mountain Lion. Does not have updated installer certificate, so system clock must be set earlier than 24 October 2019 to install.

See Also