How to Reduce System Data on iPhone is straightforward once you use the current iPhone controls. The exact wording can vary slightly by iOS version, carrier, and iPhone model.
- Open Settings > General > iPhone Storage and wait for the storage chart and recommendations to load.
- Review the largest apps and categories before deleting anything.
- Remove downloaded media you no longer need, delete large attachments where appropriate, and offload or delete unused apps.
- Restart the iPhone and install current iOS updates if System Data appears unusually large, then check storage again after the phone has had time to recalculate.
iOS does not provide a button that simply erases all System Data. Caches and temporary files are managed dynamically, so the number can change over time.