jbasudan wrote:
I bought iCloud Storage to update my MacBook to macOS Big Sur but it still says that my startup disk is too full and that I need 19 GB to update, I don't have anything saved on my laptop and I have deleted all cache files, how can I update my MacBook?
Free up space, you want to have 15-20 % free storage at all times.
You could simple try a safe boot https://support.apple.com/en-us/HT201262
to clear cache and try your update from there.
Otherwise:
Empty your Trash — Delete files and folders on Mac - Apple Support
https://support.apple.com/guide/mac-help/delete-files-and-folders-on-mac-mchlp1093/mac
How to free up storage space on your Mac - Apple Support
https://support.apple.com/en-us/HT206996
See used and available storage space on your Mac
https://support.apple.com/guide/system-information/see-available-storage-space-syspf9b375b9/10.14/mac/10.15
User tip: "Other and What Can I Do About It ?"
https://discussions.apple.com/docs/DOC-5142
Try something like OmniDiskSweeper for a GUI to get a good look at itemized file size and location:
OmniDiskSweeper http://www.omnigroup.com/more