iCloud is using space on my Macintosh HD

Open finder , in locations > Macintosh HD if you find personal documents in the upcoming column ( they could be in home folder ) , right click them and delete .

You have archived the personal documents using this way .

Open system preferences > iCloud and uncheck the box of iCloud Drive a pop up window appears , showing to keep a copy of documents , and remove from the Mac .

( a ) if you had clicked on keep a copy , they will be archived in home folder that can be viewed by clicking on finder in the dock , take cursor on top menu bar > Go > Home > your user name > iCloud Drive ( Archive ) .

See the details in the thread https://discussions.apple.com/thread/251789307

See some articles to reduce the data https://support.apple.com/en-in/HT204247

https://support.apple.com/en-in/guide/macbook-air/apdb468896e0/2019/mac/10.14.5

https://support.apple.com/en-in/HT206996

https://support.apple.com/en-in/guide/system-information/syspf5a64aa6/mac

That is the expected behaviour of iCloud Drive and "Optimise Storage": iCloud will keep any downloaded files around for some time, as long as you have enough free storage, so you avoid to download them over and over again. It will automatically remove older downloads, if you need to free storage. But if you do not want the downloads to be kept, you can remove them selectively.

• Open iCloud Drive in the Finder from the Finder Sidebar
• Then select large files or folders and ctrl-click (or right-click) them and use the command "Remove Download" to remove the local downloads of these files and folders.

This feature has been introduced on macOS 10.15 Catalina and is very convenient to give us more control over the iCloud Drive downloads.