OS X El Capitan (10.11)

OS X 10.11, a refinement-focused release over Yosemite (Metal graphics API, System Integrity Protection) — still officially downloadable via Apple's own support article for the oldest supported Macs.

legacyvery-old-hardwarestill-downloadableDownload / Upgrade ↗Official page ↗Lifecycle / Support docs ↗

Platform

MacOS

Released

September 2015

Support ends

Still supported

System requirements

MacBook (Late 2008 or later, aluminum, or early 2009 or later), MacBook Air (Late 2008 or later), MacBook Pro (Mid/Late 2007 or later), Mac mini (Early 2009 or later), iMac (Mid 2007 or later), Mac Pro (Early 2008 or later).

El Capitan focused on performance and stability polish over Yosemite's bigger visual redesign, and introduced both the Metal graphics API (which later versions would require) and System Integrity Protection, a security feature restricting what even root-level processes can modify on the system. It's one of the versions Apple's own official 'how to download and install MacOS' support article still directs eligible older-hardware owners to.

Release dates, support windows, and system requirements come from Microsoft's and Apple's own published lifecycle pages (linked above) — always confirm there before relying on this for a production/enterprise deployment decision, since support policies occasionally change.