462 files in Downloads, and the ten installers nobody needs

Downloads is where cleanup should start, not because it is the largest folder but because it is the one where nothing has sentimental value and nothing breaks. Almost everything in it was needed once, for ten minutes, and has been kept since by accident.

Disk images are always safe

A .dmg is the shipping container an app arrived in. Once the app is in your Applications folder, the disk image has no further use, and if you ever need it again it is a download away.

du -sh ~/Downloads/*.dmg ~/Downloads/*.pkg ~/Downloads/*.zip 2>/dev/null \
  | sort -h

The same argument applies to .pkg installers and to the zip archives you extracted months ago. Together these are usually the majority of a Downloads folder by size and none of them are the only copy of anything.

Sort by size, then by age

du -sh ~/Downloads/* 2>/dev/null | sort -h | tail -20

That gives the twenty largest. For the other question, which is what has been sitting there longest, sort by date instead:

find ~/Downloads -type f -mtime +180 -size +10M \
  -exec ls -lh {} + 2>/dev/null | sort -k5 -h | tail -20

That is every file over 10 MB you have not touched in six months. It is a short list on most Macs and the decisions are quick, because six month old large files are almost always installers, exports or something you already copied somewhere else.

The thing that makes it come back

Downloads refills because nothing removes anything. macOS has a setting for exactly this, in System Settings, General, Storage: emptying the Trash automatically after 30 days. It does not touch Downloads directly, but combined with the habit of dragging finished downloads to the Trash it stops the folder from growing indefinitely.

What the storage recommendations actually do covers that setting and the others alongside it, including which ones have surprising side effects.

When Downloads is not the problem

Two and a half gigabytes is a real number and it is not going to rescue a full disk on its own. Once it is dealt with, the next places to look in order are old device backups, developer output and video, which is the sequence in how to free 100 GB safely.