Following a huge special event on Wednesday, Apple released the golden master build of iOS 9 for developer testing ahead of an announced public launch date on Sept. 16.
A golden master release means Apple is testing final revisions of its upcoming iOS 9 update before an expected launch next week. Two days after iOS 9 is expected to drop, Apple plans to open sales for next-generation iPhone 6s and iPhone 6s Plus hardware, which will ship with the new operating system.
Apple is introducing a number of new features with iOS 9, including a greatly enhanced Siri virtual assistant that proactively searches surface search results, make decisions based on contextual clues, conduct deep searches and more. Smarter backend algorithms will power mock artificial intelligence capabilities to support more natural user interactions.
Along with Siri, iOS 9 brings improvements to Maps with an all new Transit feature, while other built-in apps like email and notes feature UI overhauls. A few apps, like News and Wallet, have been renamed to reflect substantial modifications to their content and operation.
As of this writing developers are receiving the iOS 9 GM in an over-the-air update.