Apple's September event was a big one. The company announced the new iPhone 18 Pro, Apple Watch Series 12 and Ultra 4, AirPods 5, and the foldable iPhone Duo. While the company certainly highlighted numerous software features for each of these devices, including some never-before-seen health features for Apple Watch, this was very much a hardware event. That's no surprise, of course: Apple reserves the vast majority of its software news for WWDC in June. But despite that fact, there was one particularly big piece of software news to come out of September's keynote: iOS 27's release date. Since Apple is using iOS 27 to advertise many of the capabilities of its upcoming devices, it makes sense that the company would need to give an ETA for the update. After all, the iPhone 18 Pro launches on Friday, Sept. 18, running iOS 27. The update would presumably need to be out by then, unless Apple intended iPhone 18 Pro users to be the first of its user base to run the software. (Spoilers: it did not intend that.) As it happens, the company officially announced the update's launch date, though it didn't advertise it heavily. At the bottom of its newsroom posts for each of its new product announcements, the company confirmed that iOS 27 will launch on Monday, Sept. 14. Developers have been beta testing iOS 27 since June, and Apple opened up the public beta one month later. Since then, volunteers have been trialing Apple's upcoming features, including Siri AI, new image editing tools, and dual-capture during FaceTime calls.Apple also confirmed that watchOS 27 will launch on Sept. 14 as well. However, at this time, it isn't clear whether Apple's other software updates, such as macOS 27 Golden Gate and iPadOS 27, will also launch at this time. If I had to guess, I would say these updates will arrive in tandem, especially iPadOS 27, but we'll have to wait for Apple's confirmation to know for sure. Which iPhones are compatible with iOS 27? Apple is supporting a long list of iPhones with iOS 27, going all the way back to 2019's iPhone 11 series. The full list is as follows: iPhone DuoiPhone 18 ProiPhone 18 Pro MaxiPhone 17eiPhone 17iPhone 17 ProiPhone 17 Pro MaxiPhone AiriPhone 16eiPhone 16iPhone 16 PlusiPhone 16 ProiPhone 16 Pro MaxiPhone 15iPhone 15 PlusiPhone 15 ProiPhone 15 Pro MaxiPhone 14iPhone 14 PlusiPhone 14 ProiPhone 14 Pro MaxiPhone 13iPhone 13 miniiPhone 13 ProiPhone 13 Pro MaxiPhone 12iPhone 12 miniiPhone 12 ProiPhone 12 Pro MaxiPhone 11iPhone 11 ProiPhone 11 Pro MaxiPhone SE (2nd generation and later)That said, some features are only available on certain iPhone models. Apple Intelligence (including Siri AI) is only accessible on iPhone 15 Pro and newer. Certain AI features, like Siri voice customization, is only available on iPhone 17 Pro and newer, including iPhone Air.