As expected, Apple says Mac OS X El Capitan will be available on tomorrow (Wednesday, Sept. 30) as a free update for Mac users.

El Capitan builds on the features and design of OS X Yosemite. Craig Federighi, Apple’s senior vice president of Software Engineering, says it “refines the Mac experience and improves performance in a lot of little ways that make a very big difference.”

El Capitan will be available at the Mac App Store. It supports all Macs introduced in 2009 and later, and some models introduced in 2007 and 2008.