System Data taking up huge amount of storage.

Hello krifos,

According to the article below, System Data will account for any data that is not otherwise categorized in your Storage settings:

System Data: Contains files that don’t fall into the categories listed here. This category primarily includes files and data used by the system, such as log files, caches, VM files, and other runtime system resources. Also included are temporary files, fonts, app support files, and plug-ins. You can’t manage the contents of this category. The contents are managed by macOS, and the category varies in size depending on the current state of your Mac. You can manage your data that falls outside the other categories using Finder or the 3rd party apps that created it.

See used and available storage space on your Mac - Apple Support

We suggest trying the guidance in these articles for freeing up storage space:

Free up storage space on your Mac - Apple Support

Find and delete files on your Mac - Apple Support

We hope that helps.

Take care!

The iCloud Drive is not an off computer storage facility. It's a syncing feature and all files in iCloud Drive are mirrored on the device. You can enable "Optimize Mac Storage" and when the free space gets down near around 20% optimized versions of new files will be stored on the local drive while full sized versions on iCloud Drive.

If you need additional storage an excellent external SSD for mobile devices is the 1TB OWC Envoy Pro mini 

I recommend drives from OWC (MacSales.com) as they have proven reliability, excellent customer support and warranties and are considered my most to be the premier 3rd party hardware supplier for Macs.