How to Update Your iPhone to iOS 27

Update over the air, in Settings

Open Settings → General → Software Update. If a newer version is available it appears here with its size and release notes; tap Download and Install, enter your passcode and let it run. The device restarts once, spends a few minutes on a progress bar and comes back on the new version.

Do it on Wi-Fi with the iPhone on a charger. iOS will refuse to begin below about 50% battery unless it is plugged in, and a large update over cellular is both slow and, on a metered plan, expensive — though it is possible, and our cellular update guide covers how.

Back up before you start, not after

An update is not supposed to touch your data, and almost always doesn't. The reason to back up anyway is the small fraction of cases where an update fails mid-flight and the fastest route back is a restore. Ten minutes of insurance against a rare but total loss is a good trade.

Settings → your name → iCloud → iCloud Backup → Back Up Now is the quickest option. A backup to a computer is more complete and, unlike iCloud, can be restored onto an older version of iOS if you ever need to go backwards — our computer backup guide explains the difference.

Free space is the usual obstacle

An iOS update needs considerably more free space than its download size, because the installer unpacks the new system alongside the one you are running before switching over. Budget roughly twice the stated download — around 15 GB for a major release.

Settings → General → iPhone Storage shows the real figure. The fastest way to find room is Offload App on a few large apps: it removes the app itself while keeping all of its data, and tapping the icon afterwards reinstalls it exactly as it was. Our storage guide covers the rest.

When no update appears

Three things cause this. Your iPhone may already be current — check Settings → General → About against the version you expected. Your model may have reached its last supported version, in which case Software Update will simply never offer the new one. Or an update is staged and has not reached your device yet; Apple rolls major releases out over days.

If your model is the question, our compatibility checker answers it for your exact device in one step, and each answer links to a full page explaining what that model does and does not get. If your iPhone is past its last version, our guide for older iPhones covers what is still worth doing.

Updating from a computer instead

Connecting the iPhone to a Mac or a Windows PC and updating through Finder or the Apple Devices app does the unpacking on the computer, so the phone needs far less free space. On a 64 GB device that is often the difference between an update that works and one that refuses to start.

It is also the more reliable route when an over-the-air update has already failed once. Our computer update guide walks through it, and if the update itself is failing rather than merely missing, our troubleshooting guide works through the causes in order.

After it finishes

Expect the first day to feel slower and the battery to drain faster than usual. That is Spotlight rebuilding its index and Photos re-analysing your library, both of which run hard for a few hours and then stop. It is normal after every major update and it resolves on its own — leaving the phone on power overnight speeds it up.

If it has not settled after four or five days, that is a different signal and worth investigating. Settings → Battery, viewed over the last 10 days, will usually identify the app responsible.

Frequently Asked Questions