It wouldn't be an Apple developer event without a big serving of fresh new software for developers to get stuck in to. Today, Apple announces the latest version of its Mac operating system: OS X El Capitan. Two big areas of focus for the new OS: experience and performance.

Apple's Craig Federighi detailed the major changes in the new release, starting off with an overhaul to the Safari web browser. You can now pin sites in the tab bar just by dragging them to the left. The address bar is also becoming the spot to find which tab audio is playing from and mute it directly. Beyond Safari, Spotlight search has been improved with the ability to respond to queries in natural language, such as asking it to find "documents I worked on in June." It can also look up weather, stocks, and games scores. There's a new Notes app as well as an improved Mission Control interface for better window management. The latter now includes a Split View, which splits the screen into two halves, one for each app.

The system font has been changed to San Francisco, to match the one on the Apple Watch, which is a change also being extended to Apple's iOS, unifying the look of its various software offerings.

On the performance front, Apple's citing some significant numbers. Apps are said to open 1.4 times faster in El Capitan, app switching is twice as fast, and PDF files open up four times faster in the Preview app. Apple is also bringing Metal to the Mac, having first introduced it on iOS last year. It supplants OpenGL for graphics rendering, offering up to 40 percent greater rendering efficiency. A good looking demo of the Unreal Engine on the new OS X was accompanied by a note from Epic Games saying the company saw efficiency improvements as high as 70 percent. Video games have generally been an afterthought on OS X, but perhaps this change with Metal could spur developers to invest more time and resources into bringing their games to Apple's desktop platform.

OS X El Capitan is available to developers today and will roll out as a free upgrade to all Mac users in the fall.