What to Sort Out Before You Move to a New Phone
Moving to a new phone goes wrong in the same three places every time: an account that was never tied to anything but the old handset, a photo library
Editorial Team · 2026-09-05
iPhone Storage Full: What System Data Is and How to Shrink It
By Editorial Team · published 2026-09-23 · updated 2026-09-23
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System Data is the grey bar at the end of the iPhone Storage screen, and it is not a bug you can delete in one tap. Apple describes it as space taken by system files, which in practice means caches, logs and buffers that apps left behind. You shrink it by removing what created it, in this order: take the three recommendations iOS offers you, offload the apps you never open, move photo originals into the cloud, then reinstall whichever single app is holding the most. Below is what each step actually frees, and what to do when the bar refuses to move.
Before you start
Open "Settings" → "General" → "iPhone Storage" and wait for the bar at the top to finish drawing. Everything below depends on that screen, and it takes a few seconds to calculate on a full phone.
Two things are worth understanding before you tap anything. Apple documents the difference between offloading an app and deleting one: offloading removes the app itself but keeps its data, so reinstalling restores your information, while deleting removes both and you start that app from scratch. And System Data is not a folder you can open — it is what is left after iOS has counted everything it can name.
Do not start by deleting photos. On most phones the photo library is the biggest single item, and there is a way to keep every picture while freeing nearly all of that space.
Step 1. Take the recommendations iOS offers
At the top of the iPhone Storage screen, iOS lists its own suggestions. The ones Apple documents are "Offload Unused Apps", "Review Downloaded Videos" and "Auto Delete Old Conversations", and which of them appear depends on what is actually filling your phone.
Offload Unused Apps is the safest of the three: apps you have not opened in months disappear from storage, keep their data, and reinstall with one tap when you next need them. Auto Delete Old Conversations removes messages and their attachments older than a year, which on a phone used for a few years is often several gigabytes of pictures people sent you once.
Step 2. Move photo originals off the phone
Open "Settings" → "Photos". If iCloud Photos is on, choose "Optimize iPhone Storage" and the phone keeps small previews locally while full-resolution originals live in iCloud.
If you would rather not pay Apple for storage, Google Photos does the same job from the other direction: back up the library, then use its own free-up-space tool, which removes local copies of items it has already uploaded. Google Photos only offers to remove a picture once the upload for it has finished, so a half-done backup cannot cost you anything. Either route leaves every picture reachable and takes the photo bar down to a fraction of its size. What neither route does is touch videos you downloaded inside other apps — those are counted against the app, not the library.
Step 3. Reinstall the app that is hoarding
Scroll the app list on the iPhone Storage screen. It is sorted by size, and the number under each name is the app plus its documents and data.
The pattern to look for is an app whose data dwarfs the app itself: a 300 MB app carrying 8 GB. Streaming apps, messengers and video editors all do this, because downloads and render caches live there. CapCut is a common offender, since every project keeps its imported clips. Tap the app, delete it, then install it again from the App Store — that clears the cache along with everything the app was holding, so export or sync anything you still need first.
This is also where System Data usually shrinks. Caches counted as system files get cleared when the app that owns them is removed.
If it does not work
The bar redraws with System Data even bigger. Give it a day of normal use. iOS recalculates in the background and the figure on the screen is often stale right after a big delete.
Offload Unused Apps is on but nothing was offloaded. It only acts on apps you have not opened recently and only when storage is genuinely low. You can offload any single app by hand from its entry on the same screen.
You freed several gigabytes and the phone still refuses to update iOS. An update needs free space for the download and the install. Keep going, or plug the phone into a computer and update from there, which needs far less room on the phone itself.
Nothing is large and the phone is still full. Back up to iCloud or a computer, erase the phone, and restore from that backup. A restore rebuilds the file system without the accumulated cruft, and it is the only reliable way to clear System Data that nothing else touches.
Bottom line
Work outwards from what you can name: the iOS recommendations first, then photos into the cloud, then a reinstall of the single heaviest app. That sequence frees more space than any cleaner app, and System Data falls on its own once the caches behind it are gone. Keep the phone above roughly ten per cent free afterwards, because that is the margin iOS needs for updates and for its own housekeeping.
