You delete videos and apps, open iPhone Storage again, and a grey bar called System Data has swallowed the space back. It has no delete button, and the internet is full of tricks that promise to empty it.
System Data is space iOS uses for caches, logs, voices, fonts and its search index; you cannot delete it directly, but you can shrink the parts that feed it. Clear Safari and large app caches, restart, install the latest iOS update, and give the phone a night on Wi-Fi and power. A full erase and restore is the last resort.
What System Data holds
Apple describes this category (shown as Other in some views) as non-removable mobile assets such as Siri voices, fonts and dictionaries, plus logs, caches, the Spotlight search index, and system data such as Keychain and the CloudKit database (Apple). It is separate from iOS, which is the operating system itself.
A few gigabytes is normal. It grows when apps cache streamed video and music, when Safari stores website data, and for a while after a major iOS update as the phone rebuilds its index.
Measure it properly
- Open Settings › General › iPhone Storage.
- Wait until the bar finishes calculating; this can take a minute or two.
- Scroll to the bottom and note the sizes of iOS and System Data.
- Write the numbers down with today’s date. You need them to see whether anything below actually helps.
The figure moves on its own as iOS clears caches when space runs low, so compare readings taken the same way.
Shrink it in this order
1. Restart
Turn the phone off, wait 30 seconds, turn it on. Recheck the storage screen after a few minutes.
2. Clear Safari website data
Go to Settings › Apps › Safari › Advanced › Website Data and tap Remove All Website Data. This clears Safari’s cache and cookies but keeps your history. You will be signed out of most websites, so check you know your passwords first. To clear history as well, use Clear History and Website Data on the main Safari settings screen (Apple).
3. Reinstall apps with large caches
Streaming video, music, podcast and social apps cache heavily. In iPhone Storage, check each large app’s Documents & Data figure. For an app that keeps everything in your online account, such as a streaming or social app, tap Delete App, then reinstall it from the App Store and sign in. Its cache starts again from zero. Offload App will not help here, because it keeps the app’s documents and data on the phone. Skip this step for any app that stores things only on the phone.
4. Update iOS
Go to Settings › General › Software Update and install what is offered. Apple fixes storage-reporting and cache bugs in point releases; Apple Community threads after the iOS 26 launch show System Data dropping after later updates for some users.
5. Give it a night
Leave the phone connected to Wi-Fi and charging overnight with the screen locked. Indexing, photo analysis and cleanup tasks run in these conditions. Check the numbers again in the morning.
6. Erase and restore, only if nothing else works
If System Data stays very large, keeps growing, or stops you updating, a full backup, erase and restore resets it. This takes hours and depends on a working backup, so follow the factory reset guide step by step. Apple Support can check for a fault before you go that far.
What does not help
| Common advice | Why to skip it |
|---|---|
| Changing the date on the phone | Can break sign-ins and sync, and any drop is temporary |
| Cleaner apps from the App Store | iOS does not let apps clear other apps’ caches or system files |
| Deleting iCloud files | Changes your iCloud account, not the phone’s System Data |
| Deleting Messages wholesale | Messages has its own category; review attachments instead with the iPhone storage guide |
When to contact Apple
Contact Apple Support if System Data grows by many gigabytes a week, the phone cannot install updates, or the steps above change nothing. Bring your dated readings, the iOS version and what you have tried.
Free space you can actually control
System Data is only one slice. The iPhone storage guide covers downloads, videos, attachments and apps, which usually return far more space.
Steps checked against Apple Support in November 2026 (iOS 26 and iOS 27). Menu names can shift slightly between iOS versions.
Sources
- Apple Support: How to check the storage on your iPhone and iPad
- Apple Support: Clear the history, cache and cookies from Safari
- Apple Community: System Data issues after iOS 26
