What is System Data on iPhone?
Short answer
System Data is space iOS uses for things like caches, logs, Siri voices, fonts, dictionaries and the Spotlight index. You can't delete it directly, and iOS clears cached and temporary files by itself when space runs low. Restarting, updating iOS and clearing big app caches can shrink it.
What's in it
In Settings › General › iPhone Storage, System Data is the gray section at the end of the bar. Apple describes this category as non-removable mobile assets like Siri voices, fonts and dictionaries, non-removable logs and caches, the Spotlight index, and system data such as the Keychain and CloudKit database. Some of Apple's support pages still call it Other.
It changes size all the time. Streaming video and music, browsing, and apps downloading content all leave caches behind, which is why it can swell to 20 GB or more and then shrink again on its own.
What can shrink it
- Restart your iPhone. Some temporary files are cleared on restart.
- Update iOS. An update can clear out old logs and caches.
- Clear Safari's cache: Settings › Apps › Safari › Clear History and Website Data.
- Offload or reinstall apps with big caches, like social media, streaming and messaging apps.
- Set Messages to keep less history: Settings › Apps › Messages › Keep Messages.
- As a last resort, back up, erase and restore. This clears everything iOS can rebuild.
What won't help
No App Store app can clear System Data or other apps' caches. iOS keeps every app in its own sandbox, so a "junk cleaner" or "phone booster" app can't reach those files. What a cleaner app can do is help with your photo library, which on most phones is much bigger than System Data anyway.
SlashPhotos only works on your photo library, and says so. For everything else, it points you to the right place in Settings.
Questions
Why is my iPhone System Data so large?
Mostly caches from streaming, browsing and apps, plus logs. It rises and falls on its own, and iOS clears cached and temporary files when space runs low.
Can I delete System Data on iPhone?
Not directly. Restarting, updating iOS, clearing Safari data and reinstalling cache-heavy apps are the ways to reduce it.
Is System Data the same as Other?
Yes. Recent versions of iOS label it System Data, and some Apple support pages still call it Other.