If you frequently work on files via Box Drive or OneDrive on your desktop then the available storage space on your local drive will gradually be reduced because they become stored in a local cache folder. 

Its good practice to occasionally clear the cache to free up local storage space on your computer. 

OneDrive

To clear OneDrive's Cache

• Right click on you OneDrive location in Explorer
• Select Free Up Space

More information around how to manage OneDrive space and making files available offline can be found on Microsoft Guidance.

Box Drive

To clear Box Drive's Cache

• Open the box drive icon on your desktop toolbar
• Go to BoxDrive Settings
• Log out of Box Drive
• Restart your computer
• Log back in to Box Drive