For some time, disk usage statistics in iOS include the “System” item, showing how much the OS itself and its auxiliary files occupy. This category also includes temporary data, various cache and other similar things.
- To check how much “System” you have, go to Settings -> General -> iPhone Storage and scroll to the bottom;

- Usually it takes about 7 GB, although quite often the partition swells up to 20 GB or more.

iPhone Storage System Size Reduce
In theory, it clears itself after rebooting the device, but sometimes this does not happen. And the system trash continues to hang dead weight. There is an unobvious and rather funny way to shrink the System section by doing almost nothing. All we need is a cable and a computer with iTunes. Here is the action plan:
- Run the iTunes app on your Mac or PC;
- Connect your iPhone to your computer with a cable;

- Click “Trust this computer” on the screen of the iOS device;
- Just wait 5 to 10 minutes;

- Unplug your iPhone and see how much the System section has shrunk;
- No need to sync your device with iTunes and generally click anything. Just plug in your gadget and wait;
- On my 64-gigabyte iPhone 6S, the result was, but not very impressive: the “System” section decreased by only 420MB. I suppose, on gadgets with a large amount of internal memory, you can get a more impressive increase – from 1 to 5GB.
Earlier, I wrote about how to clear system storage for Instagram app on iPhone can be read at this link: How to Clear Instagram Cache on iPhone?
Conclusion
Keep in mind that if a beta version of iOS 12 is installed on the device, then the method may not work. At least nothing worked for me. iTunes gave an error saying that it was necessary to update the software, but after checking it did not find any updates.
It’s the best time to ask questions and give us your feedback in comments.