The company, which scrambled to fix bugs in iOS 8 when it launched last year, says it will introduce the software update for the Apple Watch "shortly," as opposed to Wednesday.
Owners of iPhones and iPads can start moving to the next version of the software. If you have an Apple Watch, your software update is on hold.
The mobile operating system offers a bunch of new functions to predict users' needs for music, notifications and more. Apple also unveils updates to its Maps and Notes apps, and News, a news-reading app.
Commentary: Google's phone operating system has a huge problem -- and the new Android M update does nothing to fix it.
The latest data shows growing adoption for Apple's current mobile OS as iOS 9 is expected to be unveiled in June.
Letting more people test software before its final release helps Apple find bugs faster -- and potentially nip bigger problems in the bud, too.
The company's online stores were down for about 12 hours Wednesday because of an internal server error.
Update to Apple's mobile OS will add and enhance certain health features as the company gets ready to share more about its Apple Watch on Monday, according to a report.
The rate of adoption picked up steam with the release of iOS 8.1.3, which fixed some bugs and eased the software's demand for storage space on devices.
The latest update to iOS 8 reduces the amount of space needed to install an update and squashes a number of bugs.