System Data occupies 1.25 TB of my 2TB storage, leaving me with only 0.75 TB and I can save no more work.

That Storage setting display has not kept up with changes to the MacOS and software over the years and it can be very inaccurate for some users.

On my Mac, it indicates 14 GB for Music but I can see in the Finder that I have over 35 GB in music files in my Music directory.

It's even worse for Photos -- I have over 180 GB in different Photos Libraries but that Storage tool shows only 25 GB in "Photos."

In many cases, considerable email content or files associated with other programs end up classified as "System Data." Even though there is a category there for "Mail" but some large mail-associated folders can be book kept under "System Data." I had some very large many-GB sized map files and other such files associated with various Garmin devices ... these showed up in "System Data." Some Adobe-related data, catalog, or scratch files can end up being counted in "System Data."

To really audit your disk usage, you need a more capable tool, such as DaisyDisk, which is not free but when you run it as Administrator, it will show you what every MB of storage space is coming from. Some of these tools are free but I feel that the better ones require some sort of payment. In my view, they are worth it. They will show you exactly where your disk space is going.

peterfromlouth wrote:

Correction: The Free Space at the foot of the table is 6.9523 GB.

If you show only 7 GB free out of 2 TB (2000 GB), then you are running with ~ 0.35% free space. For a Mac to work properly you really need 15% free space. So you have 1/50 of the free space you should have. I am not surprised that your Mac is showing anomalies, I'm surprised it is actually operating in a usable way with that little free space.

Given that your storage is high capacity, you best option is this:

1. Backup all your files and data (Time Machine is recommended).
2. Reboot to recovery.
3. Install a fresh copy of macOS (either from internet or from an installer). This will erase your boot disk and do a clean install.
4. Reboot.
5. Restore the Time Machine backup.
6. You may have to login to some of your cloud accounts.
7. You have to give some time for the system and apps to reindex, regenerate cache, etc to perform optimally.

The Only Accurate information is found in Disk Utilities

Everything else is Window Dressing

If Free Space indicates 6.9523 GB.

Then that is what there is

The mount point of /System/Volume/Data is where your user account ( Home Folder ) is located and as such is part of the operating system

How to reduce System/Volume/Data is an often asked question

This is page 1 of 2 >> Search - Apple Community

There is no simple One Size Fit All answer for reducing this

Popular from some and not for others

The more  effective way to address this issue is to Start Over from Scratch 

For Apple Silicon computer >> Use Disk Utility to erase a Mac with Apple silicon.

For Apple Intel computers >>   Use Disk Utility to erase an Intel-based Mac followed by How to reinstall macOS

Always make a Time Machine Backup  before  proceeding 

It is also suggest to  Only Migrating the User Account and nothing more.

Emphasis on User Account Only

Reinstall the Needed and not the Wanted applications from the Apple Apps Store or Directly from the Developers 

[Edited by Moderator]

If you decide to erase your Mac's content to start over, Owl-53 provided the right instructions in the links inside their reply:

(from Owl-53's earlier post)

For Apple Silicon computer >> Use Disk Utility to erase a Mac with Apple silicon.

For Apple Intel computers >>   Use Disk Utility to erase an Intel-based Mac followed by How to reinstall macOS

And as Owl-53 noted, you need to backup your files first as you will be erasing your files from the drive. You can restore the files you need from the backup later.

Launch Disk Utility with View ➙ Show All Devices, and look for local snapshots on the boot drive. You can erase all of them except the latest.

[Edited by Moderator]

System data will manage itself.

When is the last time that you:

Made a Time Machine backup?

Cleared streaming caches?

Restarted your device?

Thanks for pointing this out.

OP must first erase his startup disk using Disk Utility from Recovery, and then proceed to do a clean install as described.

“Apple tells me to remove some TV programmes and unused applications! I have none of those. How can I rid the system of most of that System Data, so as to use the 2TB for which I paid dearly?“

———-

Ridding if System Data ima Mac:

The only way to rid of System Data 100% on a Mac is to format your hard drive, and start it all anew. And that takes some effort, such as creating a Time Machine Backup ofyour Mac > Performing the Format > Migrate items back using Migration Assistant. You might have to contact software Developers, requesting a new license key, install updates, and so on. So, perform that as a last resort.

As for your Phone or iPad:

How to Clear System Data:

Clear it using my User Tip: How to Clear "System Data" in your iPhone's Storage: - Apple Community

Sridhar Ananthanarayanan wrote:

3. Install a fresh copy of macOS (either from internet or from an installer). This will erase your boot disk and do a clean install.

Not sure where this information is coming from

That is totally incorrect

Installing from Recovery will pull down a fresh copy - Yes

But it will not Erase the Existing installation

What you describe is what we sometimes refer to " an In Place installation " or a Reinstallation

reinstallation, meaning the Fresh Copy installs Over the Exiting software and may replace missing, corrupted or otherwise Modified system files

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