Apple’s iOS 27 rollout begins on September 14, bringing Siri AI, new Apple Intelligence features, photo-editing tools and wider system changes to supported iPhones. But one detail deserves attention before users hit “Download and Install”: moving back to iOS 26 can require wiping the iPhone, and a backup created on iOS 27 cannot be directly restored to iOS 26.
Apple is beginning the rollout of iOS 27 on September 14, opening the next major iPhone software upgrade to a long list of devices stretching back to the iPhone 11 series and the second-generation iPhone SE.
The update brings some of Apple’s most significant software changes to the iPhone, including a more capable version of Siri, additional Apple Intelligence tools, new photo-editing features and updates across Maps, Health and fitness-related functions.
For users planning to install iOS 27, however, the most important preparation may have little to do with the new features.
Backing up the iPhone before upgrading matters because returning to iOS 26 is not simply a matter of changing a setting. A downgrade requires a computer-based restore that erases the device, and personal data can only be restored properly from a backup created while the phone was still running iOS 26. An iOS 27 backup cannot be directly restored onto iOS 26.
That makes the backup taken before upgrading particularly valuable for anyone who may want the option of going back.
iOS 27 rollout begins on September 14
iOS 27 becomes available from September 14 for compatible iPhones, although the update may not appear on every eligible device at exactly the same moment.
Users who do not see it immediately in Software Update can check again later. Availability can vary depending on the device and the software version currently installed.
One published estimate, based on Apple’s usual release pattern, puts availability at around 10 a.m. Pacific Time or 1 p.m. Eastern Time. That timing is an expectation rather than a separately confirmed universal release time, so users should not assume every device will receive the update at that precise moment.
The rollout also comes as Apple moves its newest iPhones onto the latest software generation.
Which iPhones are eligible for iOS 27?
The compatibility range goes back several generations. The supported models listed for the update include:
- iPhone 17 generation: iPhone 17 Pro Max, iPhone 17 Pro, iPhone Air, iPhone 17 and iPhone 17e
- iPhone 16 generation: iPhone 16 Pro Max, iPhone 16 Pro, iPhone 16 Plus, iPhone 16 and iPhone 16e
- iPhone 15 generation: iPhone 15 Pro Max, iPhone 15 Pro, iPhone 15 Plus and iPhone 15
- iPhone 14 generation: iPhone 14 Pro Max, iPhone 14 Pro, iPhone 14 Plus and iPhone 14
- iPhone 13 generation: iPhone 13 Pro Max, iPhone 13 Pro, iPhone 13 and iPhone 13 mini
- iPhone 12 generation: iPhone 12 Pro Max, iPhone 12 Pro, iPhone 12 and iPhone 12 mini
- iPhone 11 generation: iPhone 11 Pro Max, iPhone 11 Pro and iPhone 11
- iPhone SE: second generation and later
Compatibility with iOS 27 does not mean every phone on that list receives every new feature.
That distinction is especially important for Apple Intelligence and Siri AI. The newer AI capabilities require more recent hardware and are listed as available on iPhone 16 models and later, along with the iPhone 15 Pro and iPhone 15 Pro Max.
For owners of older supported iPhones, iOS 27 can therefore still be installed, but the experience will not necessarily match what is available on newer devices.
The backup detail worth checking before installing iOS 27
For most users, updating an iPhone is routine. This release comes with a reason to pay closer attention to the backup made before installation.
Anyone who installs iOS 27 and later decides to return to iOS 26 faces a considerably more involved process. A downgrade requires a Mac or Windows PC and a system restore. The restore erases the iPhone.
More importantly, a backup made after upgrading to iOS 27 cannot be directly restored onto an iPhone running iOS 26.
To recover personal data after a downgrade, the user needs a suitable backup created while the device was still on iOS 26.
The downgrade process described for iOS 27 involves connecting the iPhone to a computer, entering Recovery Mode and selecting the restore option. On a Mac, Finder can be used. Windows users can use the Apple Devices app or iTunes.
There is another limitation. Restoring an older iOS version depends on whether Apple is still signing that version. If the desired iOS 26 release is no longer being signed, a normal downgrade to that version is no longer available.
In practical terms, users who care about keeping a route back to iOS 26 should make their backup before upgrading rather than assuming a fresh iOS 27 backup will serve the same purpose later.
What to do before downloading iOS 27
Apple recommends backing up an iPhone before a major software update. That backup can be made through iCloud or with a computer.
Storage also needs attention. A major iOS update requires enough free space to download and complete the installation. Users running close to their storage limit may need to remove unnecessary downloads, videos, apps or other content first.
The iPhone should be connected to Wi-Fi, and keeping it connected to power during installation is advised. Users should also make sure they have access to their Apple Account password if it is requested.
There is a smaller but practical consideration for people who depend on their phones for work, banking or other important services. Checking that critical apps are updated and that login details are available can reduce problems after the software change.
How to download and install iOS 27
The direct route is through the iPhone itself.
Open Settings, choose General, then go to Software Update. If iOS 27 is available for the device, it will appear on that screen. Select Download and Install and follow the instructions shown on the iPhone.
Automatic updates can also be managed through Settings > General > Software Update > Automatic Updates.
A computer can be used as well. On a Mac, users can connect the iPhone, open Finder, select the device and go to General > Check for Update, followed by Download and Update.
If the update is not displayed immediately on September 14, waiting and checking again later may be all that is required.
Siri AI leads the iOS 27 changes
The most prominent software change is Siri AI, which is designed to handle more natural requests and provide more capable assistance.
The new Siri experience includes greater awareness of information on the screen and the ability to carry out actions across apps. Its availability, however, is tied to newer iPhone hardware rather than the full iOS 27 compatibility list.
Photography receives AI-related additions too. iOS 27 introduces Spatial Reframing along with an upgraded Clean Up feature for photo editing.
Apple Maps is also getting a more detailed Flyover experience using aerial imagery and Visual Intelligence models.
Health-related changes include added support for perimenopause and menopause information within Cycle Tracking. The update also expands GymKit functionality and introduces further health and fitness features.
Together, those additions make iOS 27 more than a cosmetic refresh, but the hardware requirements surrounding its headline AI functions mean the scale of the upgrade will vary significantly from one iPhone to another.
The key decision comes before tapping Install
For eligible users, installing iOS 27 itself is straightforward. The more important decision is how well the phone is prepared before the process starts.
A current backup, enough free storage, access to important passwords and updated essential apps can all matter if something does not work as expected after installation.
The unusually important point is the backup version.
Once an iPhone has moved to iOS 27, creating another backup does not replace the usefulness of a pre-upgrade iOS 26 backup for someone who later wants to downgrade. Returning to iOS 26 requires erasing the device, depends on Apple continuing to sign an eligible iOS 26 release, and requires an older compatible backup if the user wants to restore previous data.
For anyone eager to try iOS 27 on day one, spending a few minutes preparing the phone before the update could therefore be just as important as the new software itself.
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