By Jason Snell

July 9, 2015 10:28 AM PT

Summer of testing: El Capitan and iOS 9 public betas are here

Note: This story has not been updated for several years.

Today Apple’s releasing the first public betas of OS X El Capitan and iOS 9 to those who signed up to test prerelease versions of Apple software.

I’ve been using both betas, and I’ve got some of the usual caveats to give you. Though the public beta versions seem quite stable, they’re still pre-release versions of operating systems and need to be used with caution. If you’ve got a spare device, test on that. At the very least, be sure your Mac is backed up.

Also, it’s a beta! So be sure to report any bugs you find. Apple includes the Feedback Assistant app with every beta, and that’s the preferred way to give feedback about problems you encounter while testing.

OS X El Capitan’s not entirely focused on stability and performance—it’s got a bunch of user-facing features, too—but it is true that Apple is making stability and performance a bigger part of the upgrade story this year.

Apple spends a lot of time poring over anonymous crash data submitted by users and by its own metrics, the Mac is more stable than it’s been in a long time. But users have high expectations—and there’s been a wide perception that Apple hasn’t been meeting those expectations as it did in the past. Also, if you define stability as a lack of crashes, you can miss other sorts of frustrations. Looking up and seeing that your iMac is now named iMac (7) because of a networking bug isn’t a crash, but it’s a frustration.

Performance is a big part of the El Capitan story, and Apple’s making some bold claims in this area: up to 40 percent faster app launch, up to two times faster app switching, up to four times faster PDF opening, and better rendering efficiency thanks to Metal, the graphics technology introduced in iOS 8 and being brought to the Mac with El Capitan. Key Mac APIs Core Animation and Core Graphics are based on Metal in El Captain, resulting in speed boosts throughout the system—again, Apple’s claiming up to 50 percent faster rendering and a 40 percent increase in efficiency.

I’d love to say that the current public beta backs up those numbers, but as with any beta version of an operating system, it’s a moving target. The speed of an operating system can change dramatically between betas and the final version, as well as between beta versions. But Apple’s numbers are certainly encouraging.

You can read more about my experience with the El Capitan beta in a piece I wrote on Macworld today.

On the iOS side, I’ve been using iOS 9 on an iPad Air 2 and enjoying it, though currently the most intriguing features—split-screen mode and slideover—will be limited to Apple’s own apps for most users. Third-party apps have to be updated to support the features, and my understanding is that Apple’s TestFlight utility for beta-testing software (let alone the actual App Store) is not yet accepting apps designed for iOS 9.

I’ve found the most recent beta releases to be fairly stable, enough that I’m basically using this iPad as my iPad rather than the iPad mini 2 I was using before. Apps occasionally crash, but it hasn’t been anything particularly frustrating. And it’s pretty cool to watch a movie in picture-in-picture mode while I’m working on something else.

I may install iOS 9 on my iPhone, but I admit that I’m a little more skittish about that. If you rely heavily on a device, moving it to a beta can be challenging—and once you’re on the beta train, especially on iOS, it’s very hard to get back off.

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