Mail downloads and attachments: how much space Mail really uses
Mail stores messages and attachments on your Mac. Check how big it is, then reduce it from inside Mail, not from the folder.
Guides
Practical guides to Mac storage: what’s safe to delete and how to get the space back.
Articles, page 4
Is MacKeeper safe? What to check before you decide
Safety is not one yes or no. Here is what MacKeeper says about itself, and the questions to ask of any all-in-one Mac utility.
DaisyDisk vs OmniDiskSweeper vs GrandPerspective
A circular map, a sorted list and a treemap. Here is how the three differ and how to pick without guessing.
Containers and Group Containers: what they are and when to clean them
Containers hold app data, not caches. Consider removal only when all consumers are removed, retained data is inspected, and wanted data is exported and backed up.
Mac log files: where they are and which are safe to delete
Old log files are safe to remove, but they rarely hold much space. Here is where they live and what to leave alone.
Time Machine local snapshots taking up space
Local snapshots are short-term copies of your disk's state. macOS releases them when it needs room. Here is how to list them, how they differ from backups and when to act.