Another new multi-tasking feature will be picture-in-a-picture, where a video watched in full screen shrinks to a smaller size within another app when the latter is called up.
iOS 9 will support all the devices able to accept iOS 8 last year -- as far back as the iPhone 4S and iPad 2, both from 2011, both now discontinued -- without dropping the oldest, as has been the practice. "We want everyone to get iOS 9," asserted Federighi.
Cook circled back from his first moments on stage to announce native apps for the Apple Watch. "For us, this is a giant moment," he said, comparing it to 2008 when co-founder and then-CEO Steve Jobs laid out the App Store, the iPhone's stab at third-party apps. Apple dubbed the software upgrade "watchOS 2."
Outside developers will also be able to craft their own "complications," the watch industry term for the small widgets that show on a face along with the time itself, and prime real estate on the dinky screen.
With watchOS 2, users will be able to reply to email from the device, and fitness apps will be able to run natively on the Watch, not just on the partnered iPhone. Developers can also access more on the Watch, including its microphone, speaker, accelerometer and the Taptic Engine, which provides haptic feedback analogous to a tap on the wrist.
WatchOS 2 will, as with iOS 9 and OS X El Capitan, ship to developers today, and release as a free upgrade to all Watches this fall.
"From the developer perspective, watchOS 2 is a huge deal," said Dawson, "as it will make third-party apps much better."
A replay of Monday's WWDC keynote can be viewed on Apple's website.
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