How much space does a mac os update occupy after installation? I am currently running mac OS Catalina 10.15.3 and I want to update to Big Sur, however, it needs a lot of space and I am actually limited on space as I have a 128 GBs laptop (big mistake, I know), my question is: will installing this new update really take as much space as indicated (for downloading I need to free up around 15 GBs then for installing the download file I need like 20-25 GBs more), will this space be forever occupied or will the old files of Catalina be deleted and I will have relatively the same amount of space before and after updating
While installations of macOS do vary in size slightly, the previous operating system files are removed as part of the upgrade. You shouldn't expect a noticeable decrease in space available after upgrading to Big Sur.