System data

How to check the storage on your iPhone, iPad, and iPod touch - Apple Support

• System: Space taken by the operating system. This can vary based on your device and model.

You need an operating system and the associated files.

Ricanivy Said:

"System data: Why does system data take all my space on my phone this is making not wanna get anymore apple products this something we don’t need if we not going to have our space on our phones"

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Cleaning "System Data":

System Data (formerly called "Other"), basically contains unnecessary files such as caches that are used for system ease of use - all of which gather over time. Caches would be being used for remembrance of application use.  Use my User Tip: How to Clear "Other" in your iPhone's Storage - Use Backup - User Tip. 

For whatever reason, the operating system collects a lot of junk and will start deleting it as needed. With over 20 GB free you should have no problem. There might be a problem as you approach capacity, although it's supposed to clear a lot of it.

I have a 32 GB iPhone 7 and it is actually running out of capacity often. But I can't do anything because it's less than 1 GB remaining. In that case I will occasionally save to a computer, erase to factory settings, then restore from the backup. I'll often find it releases much of the system data, where junk files apparently aren't part of the backup and don't get restored.

Here is a shot of my Android phone:

System using 32.72 GB.

Modern phone OS takes up a lot space since they do a lot and have tons of features.