The first beta of OS X El Capitan was released to developers shortly following the WWDC keynote on June 8, 2015.

OS X El Capitan was released to end users on September 30, 2015, as a free upgrade through the Mac App Store.

[15] OS X El Capitan supports Metal, Apple's graphics API introduced in iOS 8 to speed up performance in games and professional applications.

[20] OS X El Capitan improves Mission Control to incorporate this feature across multiple spaces.

It also enables users to spot the pointer more easily by enlarging it by shaking the mouse or swiping a finger back and forth on the trackpad.

OS X also analyzes the contents of individual emails in Mail and uses the gathered information in other applications, such as Calendar.

For example, users can type "Show me pictures that I took in Yosemite National Park in July 2014" and Spotlight will use that request to bring up the corresponding info.

[27] OS X El Capitan has a new security feature called System Integrity Protection (SIP,[28] sometimes referred to as "rootless"[29][30]) that protects certain system processes, files and folders from being modified or tampered with by other processes even when executed by the root user or by a user with root privileges (sudo).

[31][32] Upon release, OS X El Capitan was met with positive reception from both users and critics, with praise mostly going towards the overall functionality of the new features and improved stability.

Dieter Bohn of The Verge awarded the operating system a score of 8.5 out of 10;[33] while Jason Snell of Macworld was also positive, rating it 4.5 out of 5.

[40] After the December 13, 2016, release of Security Update 2016–003, users reported problems with the WindowServer process becoming unresponsive, causing the GUI to freeze and sometimes necessitating a hard reboot to fix.