Screenshots are the lowest-friction files you create and the last ones you clean. At 2-8 MB each, a year of normal use leaves 3-8 GB of near-duplicates in the default location — and macOS names them so similarly that manual sorting is hopeless.

Where they live

du -sh ~/Desktop 2>/dev/null          # default location is the Desktop!
ls ~/Desktop | grep -c "Screen Shot"  # count them

If your Desktop doubles as the screenshot dump, that is also why Finder takes seconds to open — the desktop is a folder the system renders constantly.

Redirect them once, benefit forever

mkdir -p ~/Pictures/Screenshots
defaults write com.apple.screencapture location ~/Pictures/Screenshots
killall SystemUIServer

(Or press Cmd+Shift+5 → Options → Save to → Other Location.) New captures land in one predictable place, and your Desktop stops being a landfill.

Bulk-triage the existing pile

# screenshots older than 90 days, sorted by size
find ~/Desktop -name "Screen Shot*" -mtime +90 -exec du -h {} + | sort -h | tail -10

Review the list, delete what is obviously stale, archive the rest into a dated folder. Combined with the Desktop relocation, this typically reclaims 2-6 GB and makes the Desktop render faster immediately.

Related

Screenshots join Downloads (triage system) as the "self-growing folders" most people never audit. The heavy hitters are covered in System Data explained; the estimator ranks your own ten-second verdict.