Apple has kept OS X 10.7 Lion and OS X 10.8 Mountain Lion available for customers who have machines limited to the older software, but until recently, Apple was charging $19.99 to get download codes for the updates.
Mac OS X Mountain Lion is compatible with the following Macs:
- iMac (Mid 2007-2020)
- MacBook (Late 2008 Aluminum, or Early 2009 or newer)
- MacBook Pro (Mid/Late 2007 or newer)
- MacBook Air (Late 2008 or newer)
- Mac mini (Early 2009 or newer)
- Mac Pro (Early 2008 or newer)
- Xserve (Early 2009)
Macs that shipped with Mac OS X Mavericks or later are not compatible with the installer, however.
The $19.99 fee dates back to when Apple used to charge for Mac updates. Apple began making Mac updates free with the launch of OS X 10.9 Mavericks, which also marked the shift from big cat names to California landmark names.
Mavericks was free to download, and Apple has not charged for Mac software since then outside of the legacy Lion and Mountain Lion updates. Apple also used to have OS X 10.6 Snow Leopard available for a fee, but it is no longer purchasable.