Apple has never published a gigabyte figure for how much free space any iOS release needs, iOS 27 included. What it has published, in detail, is the difference between two storage options that get confused constantly: Offload App and Delete App.
That distinction, sitting inside Settings, is the real answer to the most anxious version of the storage question: will freeing up space before Monday cost you your data. Apple’s own wording says no, for one of the two options.
Storage tiers on this year’s iPhone 18 Pro now reach 2TB on the Pro Max as well, but the free-space question this weekend belongs to every eligible device, not just the newest ones. A phone with 2TB and a phone with 256GB read the same Recommendations screen; only the numbers behind it differ.
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Where to look before Monday
Apple’s article on freeing space for an update gives the path in three taps: open Settings, tap General, then tap iPhone Storage or iPad Storage. Scrolling to the Recommendations section surfaces Apple’s own suggestions for what to clear, generated for the specific device.
The article frames the whole exercise in one line: “If there isn’t enough space to download and install an update, manage your space with recommendations.” It does not attach a number to “enough.”
Offload App versus Delete App, in Apple’s own words
The two options read close enough on a crowded screen to be mixed up, and Apple’s definitions are the whole answer to that confusion. Offload App “frees up storage used by the app, but keeps its documents and data.” Delete App “removes the app and its related data.”
| Option | What Apple says it does |
|---|---|
| Offload App | Frees storage used by the app; keeps its documents and data |
| Delete App | Removes the app and its related data |
| Apps removed automatically during an update | Reinstalled automatically once installation completes |
| Gigabytes required for iOS 27 | Not published by Apple |
| Where to check | Settings, General, [Device] Storage, Recommendations |
The apps the installer removes on its own
There is a third, separate behavior worth knowing before Monday. Apple’s core update article notes that apps “may be temporarily removed because the software needs more space” during the update itself, and adds: “After installation is complete, those apps are automatically reinstalled.” That is a different, self-reversing action the update process can take on its own, distinct from choosing to offload something manually beforehand.
Two different kinds of storage that get confused
| Alert | What it actually means |
|---|---|
| “iPhone Storage” is almost full | Device storage; can block installing an update |
| “iCloud Storage” is full | Apple’s cloud storage; buying more does not free device space |
Apple maintains a separate article distinguishing device storage from iCloud storage, because the two “Storage full” alerts are not the same problem, and buying more iCloud storage does not free the space an update needs on the device itself. Anyone told there is not enough room for iOS 27 is being told about the iPhone or iPad, not about iCloud.
If Software Update still says there is not enough space
Apple’s documented fallback, when space stays short even after using Recommendations, is to update from a computer instead of over the air, using the Apple Devices app on Windows or the current version of macOS. Nothing in Apple’s published storage guidance involves a third-party tool of any kind.
What Apple has not said
- The number of gigabytes iOS 27 actually needs. The on-device installer states its own requirement only at the moment it needs it.
- Whether an app offloaded manually before the update behaves the same way, on reinstall, as an app the update itself removes and restores.
- Any change to the Storage screen for iOS 27. The current article’s screenshots are described as iOS 26 running on an iPhone 16 Pro.
Today is Saturday, September 12. iOS 27 arrives free on Monday, September 14, and the two days between are the ones Apple’s own storage guidance is written for, whether the fix ends up being Recommendations, an offload, or nothing at all because there was room already. The rest of this week’s announcements are gathered in our event recap.
