Downloads is the only folder on your Mac that grows on its own. Installers you ran once, screenshots named Screen Shot (47).png, ZIPs extracted and forgotten — a typical two-year-old Mac carries 20-60 GB in there, and Storage settings buries it inside "Documents" so you never see it.

The 10-minute triage (do it once, monthly after)

1. Sort by size, not date. In Finder: View → as List → Sort by Size. The top 20 items are usually 80% of the weight.
2. Kill the installers. Anything ending in .dmg/.pkg older than a week is dead — the app is either installed or not wanted. This alone frees gigabytes.
3. Three-folder rule. Make _Keep, _Archive, _Delete. Drag everything into one of the three. Anything you hesitate on goes to _Archive (decide in six months, or let it go then).
4. Empty _Delete and empty Trash. Done.

Keep it clean automatically

One Smart Folder does most of the remaining work: Finder → File → New Smart Folder → kind = Disk Image, created date > 7 days. When it shows items, they are dead installers — delete without opening. For deeper recurring hygiene (chat caches, dev caches), the guides on this site cover each location; Slack/Discord and Telegram are the usual giants.

Where Downloads ends and System Data begins

If Storage settings claims your Downloads are small but Finder disagrees, macOS is counting parts of it elsewhere — the mechanics are in System Data explained. And when you want the whole disk mapped visually instead of folder by folder, that is what DaisyDisk and friends are for; the estimator tells you first whether it is worth the trip.