Apple® announced that OS X® El Capitan, the latest major release of the world’s most advanced desktop operating system, will be available on Wednesday, September 30 as a free update for Mac® users. El Capitan builds on the groundbreaking features and beautiful design of OS X Yosemite, refining the Mac experience with updates to window management, built-in apps and Spotlight® search, and performance improvements to make everyday activities — like launching and switching apps, opening PDFs and accessing email — faster and more responsive.
Source: Apple Press Info