Excessive space consumed by "Other Volumes"

Hello!

It appears a large amount of your storage is being used by documents. I would recommend you store these in iCloud and setup "Optimize Mac Storage": Optimize storage space on your Mac - Apple Support. You may need to upgrade your iCloud storage plan: Upgrade to iCloud+ - Apple Support.

It also appears downloaded Podcasts are using a large amount of storage. If you click the information icon next to Podcasts, you can delete locally downloaded podcasts, if you aren't listening to them. You can also disable Podcasts from downloading new episodes automatically by going to the Podcasts app, then Settings > General, and disable "Download when Saving" and set "Automatically Download" to off.

If you restart your Mac in Safe mode, How to use safe mode on your Mac - Apple Support, log in, and restart back to normal mode, it may help to clear out "System Data".

Jack

Can you post a screenshot of the About this Mac ➙ More Info ➙ Storage ➙ Storage Settings (burros)?

Also take a screenshot of Disk Utility's window with the Macintosh - HD and Macintosh - Data volumes selected and post.

A lot of things, like the user Library and thus their audiobooks, and the following are listed under System data. Mine is over 200 GB because I have quite a few audiobooks ripped and stored in the user Library.

The System Data was called Other Category and consists of:

• System temporary files

• macOS system folders

• Archives and disk images (.zip, .iso, etc. - often found in the Downloads folder)

• Personal user data

• Files from the user’s library (Application Support, iCloud files, screensavers, etc.)

• Cache files: browser, Mail

• Mail messages & attachments

• Fonts, plugins, extensions

• Safari reading list

• iTunes backups

• Crud resulting from jailbreaking your iDevice

• Game data

• Saved data files

• Call history

• Notes

• Media

• Voice memos

• Other files that are not recognized by a Spotlight search

• Media files that cannot be classified by Spotlight as a media file because they are located inside of a package

• Files created and modified by other user accounts on your Mac.

They can be located anywhere on your hard drive.

The files that you have control over are located in the Documents, Downloads, Pictures, Music and Movies folders.  You can use this free app, GrandPerspective, to find the largest files on your drive so you can determine if they can be deleted or moved to an external HD for storage.

Note: you can empty the Downloads folder after the apps and/or updates that were downloaded have been installed or applied.  Some users have found a couple of Gigabytes of files in their Downloads folder which are no longer needed. 

So do what Jack-19 suggested and move some files to an external drive.