iPhone Storage Full: What System Data Is and How to Shrink It
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
Editorial Team · 2026-09-23
Phone Storage Full: What to Delete First, in Order
By Editorial Team · published 2026-09-01 · updated 2026-09-04
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Delete in this order: measure first, then the photos and video already backed up to the cloud, then app caches, then the apps you keep but never open. The measuring step is not a formality — the storage screen ranks every app by the space it holds, which turns ten small deletions into one large one. Photos and video are where the space usually is, and on an iPhone that step carries a trap: clearing them through Google Photos frees nothing at all until you empty Recently Deleted in Apple Photos afterwards. Cleaner apps are not on this list, and nothing here deletes anything you do not already have a second copy of.
Before you start
Two things decide whether this goes smoothly.
The first is whether your photos exist somewhere other than this phone. Everything in Step 2 assumes they do, and Google Photos enforces the same assumption: it will only remove local copies of items older than 30 days, so a half-finished backup cannot cost you last week's pictures.
The second is knowing what each button does. Offloading an app takes back the space the app itself occupies and keeps your documents and data. Deleting takes both. Android calls the same idea archiving. Neither one asks you twice.
Step 1. Find out what is actually using the space
On iPhone: Settings → General → iPhone Storage. A bar at the top splits usage by category, the list underneath sorts every app by size, and above both sits a Recommendations block — tap Show All to see everything the system is already offering to do.
On Android: Settings → Storage → Free up space, then pick a category. Google's own documentation says these screens differ between manufacturers, so the wording on a Samsung or a Xiaomi will not match a Pixel exactly.
Do this before deleting anything. Guessing means you can lose photos while a several-gigabyte cache sits untouched two rows further down the same list.
Step 2. Remove the photos that already exist in the cloud
Open Google Photos, tap your profile picture and choose Free up space on this device. Android confirms with “Free up [x] from device”, iPhone with “Delete [x] items from this device”. Only items that are backed up and older than 30 days qualify.
On iPhone there is a second step the app does not perform for you. What it removes lands in Recently Deleted inside Apple Photos, where it holds exactly the same space for another 30 days. Open Apple Photos, go to Recently Deleted and empty it, or the number in Settings will not move at all.
Worth knowing before you lean on this route: the 15 GB Google gives you is shared between Gmail, Drive and Photos on one account, and the unlimited tier ended in 2021. Freeing the phone this way fills the cloud instead, which is a slower version of the same problem.
Step 3. Clear caches, not whole apps
On Android every app page carries two buttons a row apart, and the difference between them is the whole point. Clear cache drops temporary files; the app rebuilds them and you lose nothing but a slower first load. Clear storage wipes the app's data permanently — logins, settings, downloads, progress.
Files by Google gathers the same temporary files in one place: open it, tap Clean, and the Junk files card offers a figure. What it removes is gone for good, so read the card rather than the number.
iPhone has no universal cache button. The two equivalents are offloading, which is Step 4, and a clear-cache switch inside an individual app's own settings — some have one, most do not.
Step 4. Offload the apps you keep but never open
An app you open twice a year holds its full install size on all the days in between. CapCut takes 809 MB on iOS. Google Photos takes 443 MB there against 60 MB on Android — the same account and the same library, seven times the download.
On iPhone: Settings → Apps → App Store → Offload Unused Apps. When space runs low the system removes apps it judges you are not using, keeps their documents and data, and leaves the icon in place with a small cloud beside the name. Tapping it reinstalls.
On Android the same idea lives in the Play Store: profile picture → Settings → General → Automatically archive apps. Archiving strips the code, the permissions and the temporary files, and keeps your data and the icon.
Neither one asks you to choose which apps go, which is what makes this the cheapest step in the list: you turn it on once and it keeps working without you.
If it does not work
The number did not move. Deleting rarely frees space at the moment you tap it, because both platforms keep a bin first. Apple Photos holds Recently Deleted for 30 days. Google Photos holds deleted items in its trash for 30 days, backed up or not. Empty the bin and look again.
Recent photos were not offered. That is the 30-day rule doing its job, not a fault. Anything shot in the last month stays on the device even when it is backed up.
Nothing appeared in Recently Deleted on iPhone. If your iCloud storage is already full, deletions skip the bin entirely and go immediately. Apple documents this, and it means the space is already back.
The largest category is called System Data or Other. Neither platform lets you delete that directly, and no installed app can safely target it. It shrinks on its own once the caches from Step 3 are gone and the phone has been restarted.
Bottom line
Measure, take the photos and video that already exist in the cloud, clear caches, then offload the apps you never open — and empty the bins afterwards, or none of it shows up in the storage screen. The one case where this order changes: if your Google account is already near its 15 GB, Step 2 only moves the problem from the phone to the cloud, and the thing to fix first is the cloud.
