The update, build number 15A263e for developers and 15A262e for public beta testers, is available through the software update mechanism in the Mac App Store and through the Apple Developer Center.
OS X El Capitan is designed to improve features introduced with OS X Yosemite, focusing on performance and user experience. A number of apps and processes on the Mac are much faster with El Capitan, and the introduction of Metal for Mac brings system-level graphics rendering that’s 40 percent more efficient.
As for user experience, El Capitan includes a new systemwide San Francisco font, a revamped Mission Control feature, a new Split View feature for using two full-screen apps at once, deeper functionality for Spotlight, and several new features for Safari, including Pinned Sites for housing frequently visited websites and a universal mute button that quiets all tabs.
OS X 10.11 El Capitan is available to both registered developers and public beta testers. Apple plans to release El Capitan to the public in the fall.