iTunes app on Mac shows iPhone storage is full the iPhone shows it is only half full

Hello JamesUUCH,

Thank you for using Apple Support Communities and thank you for sharing these details. We want to help you with your iPhone storage. You had mentioned that you're seeing iTunes show different readings for your iPhone storage, than what you see listed in your iPhone settings. The following resource can help shed light on why this might be occurring. Click here: How to check the storage on your iPhone and iPad - Apple Support

About cached files in "Other"

The Finder and iTunes categorize cached music, videos, and photos as Other instead of actual songs, videos, or photos. Cached files are created when you stream or view content like music, videos, and photos. When you stream music or video, that content is stored as cached files on your device so you can quickly access it again.

Your device automatically removes cached files and temporary files when your device needs more space.

If storage on your device differs from what you see in the Finder or iTunes

Since the Finder and iTunes categorize cached files as Other, reported usage for Music or Videos might differ. To view usage on your device, go to Settings > General > [Device] Storage.

It does mention that under certain situations, you might see data show up differently on iTunes. It suggests to view your usage by going to your device's settings. This could be expected behavior due to how Finder and iTunes categorizes data. If you feel that this might be an issue with iTunes, you an always test this issue in safe mode. This step can help isolate possible software related issues: Use safe mode on your Mac - Apple Support

If you're using a Mac with Apple silicon

1.) Shut down your Mac.

2.) Turn on your Mac and continue to press and hold the power button until you see the startup options window.

3.) Select your startup disk, then press and hold the Shift key while clicking “Continue in Safe Mode.”

4.) Log in to your Mac. You might be asked to log in again.

If you're using an Intel-based Mac

If you're not using a Mac with Apple silicon, you're using an Intel-based Mac.

1. Turn on or restart your Mac, then immediately press and hold the Shift key as your Mac starts up.

2. Release the key when you see the login window, then log in to your Mac. 

3. You might be asked to log in again. On either the first or second login window, you should see ”Safe Boot” in the upper-right corner of the window. If you can't start up in safe mode, make sure that your Mac isn't using a firmware password.

If the same thing occurs in safe mode, you might want to try reinstalling your macOS. However, if the same thing remains after all those steps, it's most likely expected as mentioned in the resource we shared with you.

We hope this helps you. Thank you for using Apple Support Communities. Take care.