iPhone storage full? What System Data is, and how to get your space back
iPhone storage full and a big chunk of it is System Data? What System Data is, why there’s no button to clear it, and the fixes that free the most space: Optimise Storage, Recently Deleted, Keep Messages and offloading apps.
HanaHow7 minute readWhen your iPhone says its storage is full, the bar in Settings often ends in a big light grey chunk called System Data. That part is the iPhone’s own working files, and there’s no button to clear it. The biggest wins are usually in Photos, Messages and apps, and the fix finder below takes you through them depending on what’s filling your space.
What’s taking the most space?
Go to Settings, tap General, then iPhone Storage, and give it a moment to add everything up. Pick the biggest part of the bar.
Restart it, then check System Data again
System Data is the iPhone’s own working files: caches, logs, Siri voices, fonts and the search index. There’s no button to clear it, and the iPhone deletes caches and temporary files itself when space runs low. A restart can sometimes bring it down a bit.
- Force restart: press and quickly release volume up, press and quickly release volume down, then press and hold the side button.
- Let go when the Apple logo appears. In iDownloadBlog’s test, keeping the side button held until the logo appeared a second time took System Data from 25 GB to 20 GB.
- Go back to Settings, General, iPhone Storage and give it a moment to recalculate.
Has System Data come down?
See this in the guideFree up space elsewhere first
The biggest wins are usually in Photos, Messages and apps. Work through these before the last resort.
Set Photos to Optimise Storage
If you use iCloud Photos, your full-size originals stay in iCloud and the iPhone swaps in smaller copies as it needs the space, starting with the ones you look at least.
- Go to Settings, tap your name, then iCloud, then Photos.
- On iOS 27, tap iPhone Storage, then choose Optimise Storage. On iOS 26 or earlier, choose Optimise iPhone Storage on that screen. US English spells it Optimize.
- Then empty Recently Deleted: in Photos, tap Collections, then Recently Deleted (below Utilities), then View Album. Deleted photos sit there for 30 days, still taking space. With iCloud Photos on, deleting them there removes them from iCloud and every device too, so only delete what you’re sure about.
No iCloud Photos? Your photos may be only on this iPhone, so copy them to a computer or another backup before you delete any.
Give it time, then check iPhone Storage again. Is there enough space now?
See this in the guideKeep messages for a year
- Save any photos, videos or chats you want to keep first.
- Go to Settings, tap Apps, then Messages. Scroll down, tap Keep Messages and choose 1 Year (or 30 Days).
- Anything older is deleted, attachments included. If you use Messages in iCloud, it goes from all your devices where it’s turned on.
- Films and series you’ve downloaded in the TV app and streaming apps count too. Delete the ones you’ve watched.
Check iPhone Storage again. Is there enough space now?
See this in the guideOffload apps you hardly use
- In iPhone Storage, the app list puts the biggest first. Tap an app you hardly use, then tap Offload App.
- It removes the app but keeps its documents and data. Tap its icon to reinstall it, as long as it’s still in the App Store, and your data comes back with it.
- To do it automatically, go to Settings, tap Apps, then App Store, and turn on Offload Unused Apps. The iPhone offloads apps you don’t use when space runs low.
Check iPhone Storage again. Is there enough space now?
See this in the guideThe last resort: back up, erase and restore
Erasing the iPhone and restoring it from a backup can bring System Data down, though Apple doesn’t promise it will. It takes time, and a backup that isn’t finished or complete can lose data, so go through every check first.
- Back up and check the backup has finished: the date and time of your last backup show under Back Up Now.
- Backing up to a computer? Tick Encrypt local backup and keep the password, or the backup won’t include your saved passwords or Health data. iCloud backups are encrypted already.
- Using iCloud Photos? In Photos, tap Collections, then your account picture, and check it’s finished syncing. Your iCloud Photos library isn’t in your iCloud backup.
- Know your Apple Account password, and move codes in authenticator apps to another device first, as they may not come back.
- Erase: Settings, General, Transfer or Reset iPhone, Erase All Content and Settings. If it asks about your eSIM, choose to keep it, or you’ll need your mobile network to reactivate your plan.
- Restore from that backup when the iPhone sets up. From iCloud, stay on Wi-Fi: apps and photos can take hours or days to come back.
More space. Keep an eye on it.
- System Data goes up and down with what the iPhone needs, so it can creep back. That’s normal.
- Paying for more iCloud storage doesn’t make the iPhone any bigger. It only frees space on the phone through settings like Optimise Storage.
- Turn on Offload Unused Apps so the iPhone makes room by itself next time.
Find what’s filling it
Go to Settings, tap General, then iPhone Storage, and give it a moment to add everything up. The bar at the top splits your storage into parts such as apps, photos, Messages, iOS itself and System Data, which is the light grey part at the end, next to any free space.
Below the bar, iPhone Storage may suggest ways to save space, such as Offload Unused Apps or, if you use iCloud Photos, Optimise Photos. Some have an Enable button; others let you review what you could delete. Under that, the app list puts the biggest apps first. iOS and System Data always sit at the very bottom of the list, whatever their size.
What System Data is
System Data is the iPhone’s own working files. Apple lists caches, logs, Siri voices, fonts, dictionaries, the Spotlight search index and system data such as the Keychain. On the iPhone, as iDownloadBlog quotes it, its description says it includes caches, logs and other resources currently in use by the system, and that its size will fluctuate according to system needs.
There’s no button to clear it. Apple says that to free up space, the iPhone removes cached and temporary files itself, and when it’s low on storage it also removes things it can download again or doesn’t need.
Restart your iPhone
A restart can sometimes bring System Data down a bit. In one iDownloadBlog test, a double force restart took it from 25 GB to 20 GB: they kept holding the side button when the Apple logo appeared, and let go when it appeared a second time. It can creep back afterwards, and Apple doesn’t document this, so treat it as a quick thing to try rather than a fix.
To force restart an iPhone:
- Press and quickly release the volume up button.
- Press and quickly release the volume down button.
- Press and hold the side button.
- When the Apple logo appears, let go.
To try iDownloadBlog’s version, keep holding the side button until the Apple logo appears a second time. Then go back to iPhone Storage and give it a moment to recalculate.
Photos: set Optimise Storage
If Photos is near the top of the list and you use iCloud Photos, make sure it’s set to Optimise Storage. Your full-size originals stay in iCloud, and the iPhone keeps smaller copies. It swaps them in as it needs the space, starting with the photos and videos you look at least, so the space comes back gradually rather than all at once.
- iOS 27: go to Settings, tap your name, then iCloud. Under Saved to iCloud, tap Photos, tap iPhone Storage, then choose Optimise Storage.
- iOS 26 or earlier: go to Settings, tap your name, then iCloud, then Photos, and choose Optimise iPhone Storage (Apple’s help page calls it Optimise Storage).
On US English iPhones it’s spelt Optimize. It’s on by default when you turn on iCloud Photos, so it’s worth checking it hasn’t been switched to Download and Keep Originals.
If you don’t use iCloud Photos, your photos may be only on this iPhone. Copy them to a computer or another backup before deleting any.
iCloud storage is separate
Paying for more iCloud storage doesn’t make the iPhone any bigger. Your iPhone comes with a set amount of storage, and iCloud storage is separate. iCloud only saves space on the phone through settings such as Optimise Storage, or Messages in iCloud, which keeps only your most recently accessed messages on the device.
Empty Recently Deleted
Photos and videos you delete sit in Recently Deleted for 30 days, still taking up space. To empty it, open Photos, tap Collections, then tap Recently Deleted (below Utilities). Tap View Album and unlock it, then tap Select, choose the photos and videos, and delete them.
With iCloud Photos turned on, deleting a photo deletes it from iCloud and all your devices, and emptying Recently Deleted removes it for good. Only delete what you’re sure about.
Messages and downloaded films
Years of photos and videos in chats add up. To delete old messages automatically:
- Save any photos, videos or conversations you want to keep.
- Go to Settings, tap Apps, then Messages.
- Scroll down, tap Keep Messages (below Message History) and choose 1 Year or 30 Days.
Anything older is deleted, attachments included. If you use Messages in iCloud, it’s deleted from all your devices where Messages in iCloud is turned on.
Films and series you’ve downloaded to watch offline, in the TV app and other streaming apps, count too. Delete the ones you’ve already watched.
Offload apps you hardly use
In iPhone Storage, tap an app you hardly use and choose Offload App. It removes the app but keeps its documents and data. The icon stays on your Home Screen with a cloud symbol, and tapping it reinstalls the app with your data, as long as the app’s still in the App Store.
To have the iPhone do this for you when space runs low, go to Settings, tap Apps, then App Store, and turn on Offload Unused Apps.
The last resort: back up, erase and restore
If System Data still takes a huge chunk after all that, the last resort is to back up the iPhone, erase it, and restore it from that backup. It’s slow, and it can lose data if the backup isn’t complete, so check each of these first:
- Make sure the backup has finished. For iCloud, go to Settings, tap your name, then iCloud, then iCloud Backup, and tap Back Up Now. Stay on Wi-Fi until it finishes; the date and time of your last backup show under Back Up Now. If it says there isn’t enough iCloud storage, the backup hasn’t completed.
- Backing up to a computer? Tick Encrypt local backup in the Finder or the Apple Devices app and keep the password somewhere safe. Without encryption, the backup doesn’t include your saved passwords, Wi-Fi settings, website history, Health data or call history, and you can’t restore an encrypted backup without its password. iCloud backups are encrypted already.
- Using iCloud Photos? Check it’s finished syncing. Your iCloud Photos library isn’t part of your iCloud backup. In Photos, tap Collections, then your account picture, to see when it last synced. A red exclamation mark means your iCloud storage is full and some photos may not have uploaded.
- Know your Apple Account password. You’ll need it to restore your apps and purchases.
- Move authenticator codes first. Codes in apps such as Google Authenticator may not come back from a backup.
To erase, go to Settings, tap General, then Transfer or Reset iPhone, then Erase All Content and Settings, and enter your passcode or Apple Account password if asked. If you have an eSIM, you’ll be asked whether to erase it or keep it: keep it, or you’ll need your mobile network to reactivate your plan.
- From iCloud: follow the setup until you reach Transfer Your Apps & Data, tap From iCloud Backup and choose your backup, checking its date and size. Stay on Wi-Fi and power. The first progress bar can take up to an hour, and your apps, photos and music keep restoring in the background for several hours or days.
- From a computer: connect the iPhone, select it in the Finder or the Apple Devices app, click Restore Backup, choose the backup you just made and enter its password.
On older versions of iOS
These steps are for iOS 27, and most work the same on iOS 26 and iOS 18. On iOS 18, open Photos, swipe up and tap Recently Deleted (below Utilities). On iOS 17 and earlier, Keep Messages is in Settings, Messages; Offload Unused Apps is in Settings, App Store; and Recently Deleted is in Photos, Albums, below Utilities.
Sources
- Apple: iPhone and iPad storage (what System Data, then called Other, contains, and Offload App), manage storage on iPhone, iCloud Photos and Optimise Storage, iCloud storage and device storage, delete photos and Recently Deleted, delete messages and Keep Messages, remove or delete apps and force restart iPhone.
- Apple on backups: back up with iCloud, back up with your Mac, encrypted backups, erase iPhone and restore from a backup.
- iDownloadBlog: see how much iPhone storage system files are taking up, with a before-and-after screenshot of a double force restart (25 GB to 20 GB). AppleInsider: how to fix System Data filling your iPhone’s storage. Macworld: how to free space on iPhone.
Read the video transcript
Your iPhone's full, and loads of it is System Data? Here's what that is, and how to get your space back. First, find what's filling it. In Settings, tap General, then iPhone Storage, and give it a moment to add everything up. The bar at the top splits your storage into apps, photos, iOS itself, and System Data, the light grey bit at the end. System Data is the iPhone's own working files: caches, logs, and things like Siri voices, fonts and the search index. Apple says it goes up and down with what the system needs, and there's no button to clear it. When space runs low, the iPhone deletes caches and temporary files on its own. Restarting can sometimes bring it down a bit. In one iDownloadBlog test, force-restarting twice took it from twenty-five gigabytes to twenty, though it can creep back. The biggest wins are usually elsewhere, though, and the app list below puts the biggest first. If Photos is near the top and you use iCloud Photos, check it's set to Optimise Storage. It's in Settings: tap your name, then iCloud, then Photos, and on iOS 27, iPhone Storage. Your full-size originals stay in iCloud, and the iPhone swaps in smaller copies as it needs the space. Paying for more iCloud storage doesn't make the iPhone any bigger, by the way. They're separate, and iCloud only saves space on the phone through a setting like that one. Photos you delete sit in Recently Deleted for thirty days, still taking up space, so empty it once you're sure. Next, Messages. Years of videos in chats add up. In Settings, Apps, Messages, Keep Messages can delete anything older than a year, attachments included, on all your devices if you use Messages in iCloud, so save the ones you want first. Films you've downloaded in streaming apps count too, so delete the ones you've watched. For apps you hardly use, tap one in the list and choose Offload App. It removes the app but keeps its documents and data, and it all comes back when you reinstall, as long as the app's still in the App Store. Offload Unused Apps, in Settings, under Apps, then App Store, does it for you when space runs low. If System Data still takes a huge chunk after all that, the last resort is to back up the iPhone, erase it, and restore it from that backup. Make sure the backup's finished, and if it's on a computer, tick Encrypt local backup, or your passwords and Health data won't come back. The written guide has a storage fix finder that takes you through it, depending on what's filling your space. That's HanaHow. See you next time.
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