iOS 27 arrives on Monday, September 14, and the one job worth finishing before you tap update is a backup you have actually confirmed completed. On a full iPhone it takes longer than people expect, which is why it belongs to Sunday evening rather than to Monday morning.
Apple Support’s current step lists for backing up an iPhone are written against iOS 26, the version selector at the top of the guide says so, and the exact menu names may shift once iOS 27 ships. The checklist below is therefore arranged by what to confirm rather than by which buttons to press, so it survives the change. Our iOS 27 release date roundup has the confirmed dates.
Key facts: the update, and what Apple has published
| Item | Detail |
|---|---|
| Update | iOS 27, Monday, September 14, 2026, free |
| Compatible iPhones | iPhone 11 and later, plus iPhone SE (2nd generation and later) |
| Download size | Not published by Apple |
| Install time | Not published by Apple |
| Release time | Not published; Apple’s iOS updates usually appear around 10 a.m. Pacific |
| Step lists | Apple’s published backup guide is currently written for iOS 26; paths may change on September 14 |
| Route back to iOS 26 | Apple has not published one |
The checklist, in order
| Order | What to confirm | Why it matters |
|---|---|---|
| 1 | Your iPhone is on Apple’s iOS 27 list | The list starts at iPhone 11 and iPhone SE second generation, not iPhone 12 |
| 2 | You know your Apple Account password and can pass two-factor authentication | A backup you cannot sign in to restore is not a backup |
| 3 | Free space on the device | Apple has not published the download size, so leave more headroom than you think you need |
| 4 | The backup reports a completed date and time | A progress bar is not a finished job |
| 5 | Anything that lives only on the phone is also somewhere else | Downloads, voice memos and documents saved locally deserve a second copy |
| 6 | Power and a network you trust | Apple has not published an install duration |
| 7 | Find My and sign-out, only if this device is going to trade-in | Apple’s Trade In preparation is back up, turn off Find My, sign out |
Item four is the one people skip. Starting a backup and walking away is not the same as finishing one, and the difference only becomes visible at the worst possible moment. Open the backup screen again after dinner and read the timestamp.
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Start it on Sunday, not on Monday morning
Monday is a heavy day for Apple’s servers. iOS 27 ships alongside iPadOS 27, macOS 27 Golden Gate, watchOS 27 and visionOS 27, all on September 14. Apple has not published a release time for any of them, and its iOS updates have typically appeared around 10 a.m. Pacific, which means a great many devices reach for the same network at once.
Doing the backup on Sunday also separates the two failure modes. If the backup is slow, you find out on a day when nothing depends on it. If the update is slow, your data is already safe.
If a new iPhone or Apple Watch is arriving this month
Two purchases change the sequence. Apple Watch Series 12 lists an iPhone 11 or later running iOS 27 or later as a requirement, so if you pre-ordered on September 12 for a September 18 delivery, the update has to happen first. iPhone 18 Pro comes the other way around: Apple ships it with iOS 27 installed and a 1 metre USB-C cable in the box, so the phone is already current when you open it.
Trade-ins get their own backup. Apple’s Trade In page says an estimate is valid for 14 days after you receive the new device, that a specialist evaluates the device in store and the credit may differ from the online estimate if the condition does not match what you described, and that its preparation steps are to back up, turn off Find My and sign out. Apple lists processing at two to three weeks, with credit following in three to five business days. Our iPhone 18 Pro pricing breakdown covers what that credit is set against.
What a backup does not solve
A backup protects your data. It does not protect your expectations, and several of the iOS 27 headlines are gated in ways no amount of preparation changes. Siri AI is a beta, in English first, with French, Japanese, Korean, Portuguese and Spanish following in October. Apple Intelligence covers 16 languages, counting Simplified and Traditional Chinese separately.
Apple also says Siri AI will not be initially available in the EU on iOS, iPadOS and watchOS, that the new Apple Intelligence features are unavailable in China pending regulatory requirements, and that server-backed features carry daily usage limits. Messages Suggestions and the Passwords tool that flags and updates weak credentials are both labelled as coming in a future software update.
What Apple has not said
Apple has not published the iOS 27 download size, the install time, the release time, or a supported way to return to iOS 26 after updating. It has not published iOS 27 versions of its backup step lists, which is why the guidance above is written around what to verify. Third-party app compatibility is not published in advance either.
Back up on Sunday, September 13, confirm the timestamp, then update on Monday, September 14. If a new device is coming on Friday, September 18, keep its trade-in preparation as a separate job later in the month.
