How to Clean Startup Disk on Mac

Mac asks to clean startup disk when storage is almost full

Step 1. Apple menu → About this Mac

Step 2. Click on the storage tab

Step 3. Click on Manage

Step 4. See the recommendations

a. Store in iCloud → This frees up space from mac and puts files in iCloud. You can choose what all goes to the cloud among the options given.
This will not delete your files, just store an optimised version wherever applicable.

b. Click on Optimise storage to automatically delete videos after watching from iTunes

c. Empty trash automatically after 30 days

d. Click on review files to see files ordered from largest to smallest and delete redundant large files