Reducing system data storage on MacBook Pro

300GB doesn't necessarily indicate a problem.

It's only a problem if free space gets too low, and at that point the OS will delete data that it deems unnecessary.

Much of the 'System Data' is used by caches, indexes, Time Machine snapshots, etc.... stuff that doesn't fall into the typical 'Application/Data/Media' buckets, and stuff that you don't interact with directly, but that the OS uses to improve performance (such as caches and indexes) or enhance the user experience (instant recovery of recently-deleted data via Time Machine). Data in this bucket is considered transient - caches can be rebuilt, indexes can be recreated, Time Machine backups can be offloaded to external media, etc.) so, for the most part, just let the OS do its thing.

MatteoGiuliano wrote:

I always face a big problem.

I have a MacBook M4 Pro with 1 TB of storage space, but Apple takes up at least 300 GB with system data. How can I reduce the size of this data?

As others have pointed out, "System Data" can include a mix of system generated files as well as user files. It's not a helpful category.

A better sense of were your disk space is going is provided by apps like DaisyDisk (which is a paid up app, but some others are free or paid up). I like DaisyDisk because when run with administrator privileges, it has a clear interface that allows you to drill down and quickly determine exactly where your disk space is going. The administrator privileges part is important because some files may be hidden or not visible normally. Also, DaisyDisk calls out space taken by coaches and Time Machine snapshots as well as other things that take up space.

After you have tried everything else you can erase and reinstall os and migrate files which will reduce that number to start cycle once again. I have done that on several Macs.

System Data is mainly your own data that Spotlight cannot assign to a category (one common example is email attachments stored by Outlook). See this User Tip:

How to free up ‘System Data’ and other st… - Apple Community

Apart from what my colleague has rightly mentioned 👍

300 GBs of 1 TB equals only 30% of the Entire Drive Capacity as Used Space

That, in a of itself, is will within the often suggested values of 15 %- 20 % of the Entire Drive as Free Space

Some have even mentioned keeping only 100 GB to 200 GB as Free Space

So, where exactly is the issue / problem ?

Does the computer have a specific issue that requires additional investigations ?

If so, suggest you give us some Technical Details of what it is or what they are