RoomForGemsYou open Settings, look at your storage, and see a big grey bar called System Data. Sometimes it is 10 GB. Sometimes it is much more. You did not put it there, and there is no delete button. This guide explains what it is, what you can do, and what nobody can do for you.
What System Data actually is
System Data is the space iOS uses for its own working files. On older versions of iOS, and on a computer, it was called "Other". Macworld notes the rename, and Apple's own help page still describes the same contents under "Other".
Apple says this category holds:
- Non-removable resources such as Siri voices, fonts and dictionaries.
- Non-removable logs and caches.
- The Spotlight search index.
- System data such as the Keychain (your saved passwords) and the CloudKit database.
Macworld adds that streaming caches from music and video, plus Safari and Messages caches, also count toward it. When you stream a song or a show, the phone keeps a temporary copy so it loads faster next time. Apple says these cached files are removed when the device needs more space.
Why it goes up and down
System Data is not a fixed size. It grows when you stream, browse and send photos in Messages. It shrinks when the phone tidies up after itself.
Apple puts it simply: when your device is low on storage, it removes cached and temporary files "so you don't have to." Macworld says 5 GB to 20 GB is typical, and that well over 20 GB may mean it has grown out of hand.
So a large number is not always a problem. It is often space the phone is borrowing and will give back.
Why no app can clear it, including ours
This is the part many cleaner apps leave out.
Apple's security guide says all third-party apps are sandboxed. Each app gets its own private folder. It cannot reach into other apps' files. And Apple says "system files and resources are also shielded from the users' apps."
That means no app from the App Store can open System Data, let alone empty it. If an app promises to "clear System Data" or "clean system files" on an iPhone, it cannot keep that promise. At best it is clearing its own temporary files, or showing you a number that looks good.
If you paid for an app like that, see how to cancel a cleaner app subscription and ask for a refund.
What genuinely helps
None of these are magic. They are the steps that work with how iOS is built.
1. Wait and let it settle
After an iOS update, a big restore, or a lot of streaming, System Data can look huge for a while. Give it a day or two of normal use and check again (not verified). The phone clears caches when it needs the room.
2. Restart the phone
Turn it off and on again. Many people report System Data drops a little after a restart (not verified). It costs nothing and is safe.
3. Keep a few GB free
iOS works best with some breathing room. Keeping a few gigabytes free gives it space to update and manage its caches without a struggle (not verified). Macworld notes that a full iPhone can stop iOS updates from installing.
4. Clear Safari's website data
Apple's steps on current iOS:
- Open Settings, tap Apps, then tap Safari.
- Tap Clear History and Website Data.
- Choose how far back to clear, then tap Clear History.
Apple says this does not change your AutoFill details. You may need to sign in to some websites again. If you want to keep your history, use Settings › Apps › Safari › Advanced › Website Data › Remove All Website Data instead. Macworld also suggests closing tabs you no longer need.
5. Trim Messages
Photos and videos in your texts add up. Go to Settings › General › iPhone Storage › Messages to see what is there. Macworld suggests changing the Message History setting from Forever to 1 Year or 30 Days. Read this carefully first: older messages and their attachments will be deleted. Save anything precious before you change it.
6. Offload or delete heavy apps
In Settings › General › iPhone Storage, tap an app to see its size. Apple explains the two choices:
- Offload App frees the space used by the app but keeps its documents and data.
- Delete App removes the app and its related data.
Apps that keep big caches, such as podcast or video apps, can shrink a lot when deleted and reinstalled. Macworld gives Podcasts as an example.
7. Update iOS
Install updates in Settings › General › Software Update. Updates sometimes fix bugs that make caches grow too large (not verified).
The last resort: back up and restore
Macworld calls this the most involved option, and the most effective. You back up the iPhone, use Erase All Content and Settings, then restore from the backup.
Please be careful here:
- Make sure your backup is complete and recent before you erase anything.
- Check that your photos are really in iCloud or on a computer.
- It can take hours.
- Some of the System Data may come back after you restore from a backup (not verified).
If you are unsure, ask a family member or an Apple Store to help. There is no rush.
On Android: "System" is the operating system
Android phones show storage by category under Settings › Storage, and one of them covers the system itself. This is mostly Android. PCWorld found system files taking 15 GB to 28 GB on different phones. As PCWorld put it, "Clear cache and restart all you want, that space isn't coming back." (PCWorld, read on 10 October 2026.)
You cannot delete it, and neither can any app. Focus on photos, videos, downloads and apps instead.
Where we fit, honestly
RoomForGems cleans photos and videos only. It helps you find the ones you no longer need, and you choose what goes. It does not touch System Data, and it cannot. We list everything it can't clean on what we can't clean.
It costs $9.99 once, with no subscription. If photos are what fill your phone, start with how to delete duplicate photos or our wider guide, iPhone storage full: what actually works.