iOS 27 is now available for compatible iPhones, but there is no requirement to install Apple’s latest major software update the moment it appears in Settings.
If you decide not to update immediately, your iPhone will continue running its existing version of iOS. Apps, calls, messages and other everyday functions do not suddenly stop working simply because a new major iOS release has become available.
There are trade-offs to remaining on an older version, however. iOS 27 contains new features, improvements and security changes that are unavailable to devices remaining on iOS 26.
Apple can continue providing some security updates for previous iOS versions, but support for older releases changes over time. Staying indefinitely on an outdated version can eventually mean missing security fixes and losing compatibility with apps that raise their minimum iOS requirements.
If your reason for waiting is concern about early bugs, delaying the update for several days can be a reasonable middle ground. It allows time for wider feedback while avoiding remaining on old software indefinitely. We’ve looked separately at whether you should install iOS 27 immediately or wait.
Not every iPhone can install iOS 27. Apple supports iPhone 11 and later with the release, while older models remain limited to the software versions available for their hardware. Our compatibility guide lists every supported iPhone.
There is therefore little reason to panic if you do not update on launch day. The more important consideration is avoiding leaving a supported iPhone on outdated software indefinitely, particularly once important security updates and app compatibility begin moving forward.