OS X El Capitan
OS X El Capitan (/ɛl kæpɪˈtɑːn/ el-KAP-ɪ-TAHN) (version 10.11) is the twelfth major release of OS X (now named macOS), Apple Inc.'s desktop and server operating system for Macintosh computers. It is the successor to OS X Yosemite and focuses mainly on performance, stability and security. Following the Northern California landmark-based naming scheme introduced with OS X Mavericks, El Capitan was named after a rock formation in Yosemite National Park, signifying its goal to be a refined version of Yosemite. El Capitan is the final version to be released under the name OS X; its successor, Sierra, was announced as macOS Sierra. El Capitan received far superior reviews when compared to Yosemite.
The first beta of OS X El Capitan was released to developers shortly following the 2015 WWDC keynote on June 8, 2015. The first public beta was made available on July 9, 2015. There were multiple betas released after the keynote. OS X El Capitan was released to end users on September 30, 2015, as a free upgrade through the Mac App Store.