Mac OS eating up drive space

This looks like a “memory leak”: some application may be requesting more and more memory from the system and never releasing it. The system would use up space on the drive as virtual memory until you face “your system has run out of application memory” and you have to restart.

Open Activity Monitor and keep an eye on the memory pane. Do you see an application using multiple GB? Is Swap Space growing a lot?

It is generally a good computer practice to alway keep at least 20% to 25% of the Total Drive Capacity’s as Empty Space.

Allowing the computer to drop below these guidelines may eventually, cause unintended consequences.

There is Purgeable Space and there is Empty Space.

Purgeable Space which is Controlled by the Operating System. When the Operating Systems decides the computer needs additional Empty Space, it will move a portion of the Purgeable to Empty space

AFAIK - there is no User Actions to hasten this transition from Purgeable to Empty Space

It can day or longer before this will occur.

The links below will assist in identifying what is taking up space on the Internal Drive and provide possible ways to remove data that is under the direct control of the User ( Home Folder ) . 

Rebuild the Spotlight index on your Mac

What is “Other” storage on a Mac, and how can I clean it out?

Free up storage space on your Mac

GrandPerspective 

➡️ How to delete Time Machine snapshots on your Mac.  

Often caused if the Time Machine Drive has not been attached  to the computer and TM Backup is set to run on a Schedule. 

TM Backup will make Snap Shot on the Internal Drive awaiting the TM Backup Drive to be attached. 

Only then will the Snaps Shots be transferred to the External Drive and deleted the Internal Drive. ⬅️

See used and available storage space on your Mac

Locate backups of your iPhone, iPad, and iPod touch

Is there a Suite of Adobe Application used on this computer ?

They may create some very large cache files that can be removed. Though, the Adobe cache files will be recreated as the Applications needs them.

https://helpx.adobe.com/ca/premiere-pro/kb/clear-cache.html

The final word from Apple on Managing the " Other/ System Data “ Category

Other / 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.

To add to the very good advise by previous Contributor

Use the Activity Monitor application and make sure to use View >> View All Processes 

What process or processes are using the Most CPU  and Memory.

Often times - the issue maybe not a single Process alone but a combination of Processes

Also, when the computer is using so much Memory - it can be a indicator of a Lack Of Empty Spaces on the Drive.

In which case, the CPU and Memory usage would become Much More because it is searching for Empty Space to save all the Changes the user is performing.

Also, depending on the number of  Open Tabs in your Browser, they can also affect Memory Usage.

Get into the habit of shutting down your Mac rather than leaving it on all the time, this will allow housekeeping to take place on startup. Silicon Macs boot up in seconds so this shouldn't be an issue.

Mal-S wrote:

Get into the habit of shutting down your Mac rather than leaving it on all the time, this will allow housekeeping to take place on startup. Silicon Macs boot up in seconds so this shouldn't be an issue.

Besides the debate on whether to sleep or shutdown: what the OP is experiencing, in that more than a hundred GB of drive space are eaten up in a few hours, is NOT normal. Space on the system drive can fluctuate a bit with use, but it disappearing at this speed indicates that something is definitely wrong, and he is doing well to try to troubleshoot this. Then if he so chooses, we may adopt your policy (I don't have anything against it, except that it should not happen out of necessity).