iOS 15 is compatible with a wide range of devices, from the iPhone 6S, released in September 2015, to the latest models in the iPhone 12 series. However, not all phones receive all the new capabilities that Apple introduced at WWDC 21 for the new operating system. Some models will receive only a few new features, interface changes, and some of the functionality of the new, updated Apple applications.
Here's what's missing from iOS 15 on some older iPhones
New AI processing capabilities, or require better graphics chips, will only run on newer models. Thus, some functions related to Siri, playback or recording of processed sound or video calls via FaceTime will be available only on the last few generations of iPhone, Gizmodo announces.
FaceTime
The native video calling application from iOS, iPadOS and macOS, FaceTime, gets some new features, including the ability to integrate with calendar applications, as well as browser access, for alternative operating systems such as Android or Windows. However, the top features will only be available on Apple devices that have the necessary hardware.
One of these abilities is Portrait Mode, the ability that separates the subject from the background and adds a blur effect around the person. This capability will only be available on devices that have Face ID hardware. Also, Spatial Audio, which is the playback of the sound in the direction in which it is displayed on the screen, will only work on newer models, which allow the use of this function.
Apple Maps
Apple Maps services are constantly improving, but they are far behind the alternatives from Google and other competing companies. Apple will implement an AR navigation mode for Apple Maps, but it will only be available on newer device models. Also, in order to use the display mode similar to Google Earth, which renders the entire planet in 3D, you will need an iPhone with Apple A12 processor, ie from the XR / XS generation to the newer variants, such as iPhone 11 and iPhone 12.
New 3D details on maps, such as buildings and tourist attractions, will also be limited to newer smartphone models.
Digital Keys
In the case of digital keys, Apple limits this feature to devices that have the necessary hardware. Not only NFC is needed, which integrates all iPhone models from 6 to now, but also a UWB (ultra wide-band) sensor, which detects the proximity of other devices. Thus, again, only iPhone XS / XR or newer phones will be able to use this capability.
Local AI functions
When it comes to AI capabilities, Apple will only allow devices with the A12 Bionic chipset or later to access them. Thus, iPhone X or 8 and older models will not be able to use the new Live Text features, which recognize text in photos. Also, photo recognition features, such as dog breeds, or various objects (Google Lens-style), will only work on the last three generations of iPhones on the market.
The same thing happens with Siri. The virtual assistant will only be able to run locally, ie without the internet, on devices with an A12 processor or newer. Also in the Siri chapter are the new wizard customization features and the ability to dictate text without being connected to Apple servers.
Other
But a weird limitation is that it doesn't let you zoom in if you're shooting using QuickTake capability, which involves holding down the capture button in photo mode. Also, the 3D weather effects in the new weather app will not appear on older devices.
And "health" capabilities lag behind older iPhone 8 models. Those who want to gauge how "straight" they are with iPhone sensors won't be able to do so on the iPhone 7 or 6S.
However, there is a feature that will only be missing from the iPhone 6S, as all models are compatible with the iPhone 7: Dolby Atmos and 3D sound effects when using AirPods Pro or AirPods Max.