OS X 10.11 El Capitan was released on September 30, 2015, as a refinement-focused update to OS X Yosemite. While it maintained a similar visual style, it introduced critical performance enhancements and several multitasking features that defined the later OS X era. Mac OS X 10.11 El Capitan: First Impressions
Apple provides the full installer for older macOS versions through their support pages. Download OS X El Capitan : This link leads to a page where you can download the InstallMacOSX.dmg : Once downloaded, you must open the and run the Mac Os X 10.11 El Capitan Iso Download