Today Apple formally announced OS X El Capitan, the next version of its desktop operating system.

Apple says it will release this next version of OS X to developers today, then to the public in beta this July. A final, more stable version of the OS will launch this fall, as usual.

Apple also announced today that over 55 percent of Mac users are running the latest version, OS X Yosemite. Craig Federighi, Apple’s senior vice president of software engineering, said on stage that this is the “fastest adoption rate of any desktop OS ever.”

Here’s a first look at the new OS, which includes improvements to Safari: pinned sites and muted tabs;

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Apple Mail: tabbed mail windows and gestures;

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and Spotlight: expanded search features to include stuff like weather data.

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Apple also shared that its graphics technology, Metal, is coming to the Mac.

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Split full-screen browsing, Microsoft Surface-style, is another new El Capitan feature.

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What’s new?

As we wrote last week, Apple’s biggest changes to OS X version 10.11 will be under the hood. The OS, revamped annually at the Worldwide Developers Conference (WWDC), will feature new security and stability features, contrasting the more cosmetic, feature-centric updates made last year with the launch of OS X Yosemite.

It had been previously reported that Apple planned to debut a new security system, Rootless, to “prevent malware, increase the safety of extensions, and preserve the security of sensitive data,” according to 9to5 Mac.

Security has clearly been top of mind for Apple chief executive Tim Cook. Just last week, Cook spoke in Washington, D.C. about the company’s concern for its users’ information.

I’m speaking to you from Silicon Valley, where some of the most prominent and successful companies have built their businesses by lulling their customers into complacency about their personal information. They’re gobbling up everything they can learn about you and trying to monetize it. We think that’s wrong. And it’s not the kind of company that Apple wants to be.

Beyond security, we anticipated that Apple would somehow expand its existing Handoff features. Last year, Yosemite enabled iPhone users to receive phone calls, send text messages, and finish up emails started on their iPhones from their Macs. iPhone-Mac connectivity has been a trend since 2012’s Mountain Lion brought iMessages to Macs. Now, with the Apple Watch on board, we expect more interoperability between the three devices.

Apple was also expected to finally add its Control Center panel, currently an iOS-only feature, to OS X.

Apple shared the news above during its annual WWDC in San Francisco.