My iPhone 15 normally has about 20GB of free space, but over the past month the storage gradually filled up completely. I recently deleted roughly 10GB of photos and videos, and I haven't recorded anything new since then, yet the free space disappeared again within two days. In Settings, System Data is showing around 69GB. What could be causing this, and is there a safe way to reduce or clear System Data without losing important files?
3 Answers
This sounds like an iOS storage glitch, especially since the space returned after deleting photos without any new media being added. Make a current backup, then restore the iPhone using a computer. A full backup-and-restore process is often the safest way to clear abnormally large System Data, but verify the backup before erasing the phone.
If the storage is being consumed by Mail data, removing the configured email accounts and adding them again can force iOS to clear and rebuild the local mail cache. It’s worth checking the storage breakdown first, though, since this won’t help if Mail is only using a small amount of space.
Did this start after updating iOS? A failed update, cached files, or a system indexing problem can sometimes make System Data grow unusually large.
Yes, I installed the iOS 27.0 public beta when it was released, so that could definitely be related.

I checked Gmail, and it’s using less than 1GB, so the missing space seems to be coming from somewhere else.