Uninstalling an app on a Mac is two moves: drag app to Trash. And that’s a lie. Behind the app bundle you just trashed live caches, preferences, application support, saved state, login items and container folders — sometimes several hundred MB per app, forever.

Microsoft 365 leaves gigabytes. Old photo editors leave FaceData caches. Every app you’ve “removed” over three years may still own 10 GB of your SSD in ~/Library. Here’s how to find them and delete them — without nuking your sister’s preferences by accident.

Where app leftovers hide

An app’s real footprint is scattered across macOS:

Location	What lives there
`/Applications/<App>.app`	The bundle you do delete
`~/Library/Application Support/<App>/`	App data, docs, DBs
`~/Library/Preferences/<bundle-id>.plist`	Settings
`~/Library/Caches/<App>/`	Caches
`~/Library/Saved Application State/<bundle-id>.savedState/`	Window state
`~/Library/Containers/<bundle-id>/`	Sandboxed app data (Mac App Store apps)
`~/Library/Logs/<App>/`	Logs
`~/Library/LaunchAgents/`	Background items
`/Library/LaunchDaemons/`	System-level helpers

Find leftovers by name

After “uninstalling” <App>, search for its name and bundle ID:

# by display name
find ~/Library -iname "**" -maxdepth 3 2>/dev/null

# by bundle id (e.g. com.company.AppName)
find ~/Library -iname "*com.company.*" -maxdepth 3 2>/dev/null

# list biggest leftovers
du -sh ~/Library/'Application Support'/* 2>/dev/null | sort -rh | head -20

The last command is the eye-opener: open ~/Library/Application Support and sort by size — the apps you deleted years ago are the ones you’ve kept assuming you’d reinstalled.

Safe to delete? Rules of thumb

After quitting the app (⌘Q), leftovers for a current app are mostly cache → safe.
After fully uninstalling the app: exit it, then remove its ~/Library name-match leftovers → safe (it’s broken/removed anyway).
NEVER delete ~/Library/Preferences, Application Support or Containers for installed apps by hand — you’ll lose settings/data.
Skip anything under ~/Library/Application Support you don’t recognize if it belongs to an installed app you use.

So the procedure differs for:

a) apps you’re genuinely dumping → delete the whole family of name-matching folders,
b) apps you keep → only their Caches/ and Logs/ are disposable (see ~/Library guide).

The safe uninstall sequence (for a full removal)

# 1. quit it
osascript -e 'quit app ""' 2>/dev/null

# 2. remove the bundle (moves to Trash, reversible)
sudo rm -rf /Applications/".app"
# (or drag to Trash manually if you want undo)

# 3. remove name-matching leftovers
rm -rf ~/Library/Application\ Support/""
rm -rf ~/Library/Preferences/com.company..plist
rm -rf ~/Library/Caches/""
rm -rf ~/Library/Logs/""

Replace <App>, com.company.<App> with the real values (find them with the find step above). This leaves no footprint — and your other apps are untouched.

App Store apps: Containers

Mac App Store (sandboxed) apps store everything in:

~/Library/Containers//
~/Library/Group Containers//

Deleting the app from Launchpad doesn’t clear these for most apps. After uninstalling, rm -rf ~/Library/Containers/<bundle-id> reclaims the often-large sandbox.

The (very) common culprit: IDEs & dev tools

The worst leftover offenders are developer tools — each Xcode metadata, each Android SDK, Docker, each node runtime leaves GBs. After uninstalling one, check:

~/Library/Developer/ (Xcode leftovers — DerivedData guide)
~/.gradle, ~/.m2, ~/.cargo, ~/.npm (see node_modules, Homebrew cache)
~/Library/Application Support/Google (Android Studio — guide)

Reason #1 to see it before you delete

The danger of “delete leftovers” is accidentally touching an installed app’s real data. The safe workflow is identify → verify → trash. A disk analyzer that shows per-folder byte counts under ~/Library/Application Support and ~/Library/Containers turns that from guesswork into a 10-second glance.

DiskInsight ranks every folder by real bytes (including hidden containers), stages what you pick to the macOS Trash — reversible, reviewable — and never, ever offers your real data to the delete button. 100% local, no telemetry, one-time price.

TL;DR

Uninstalling = app bundle only; the rest hides in ~/Library.
find ~/Library -iname "*<App>*" + the Application Support size sort to locate leftovers.
For dumped apps: remove the name-family (bundle → Application Support → Caches → Logs → Containers).
For kept apps: only their caches/logs are fair game.

Clean, uninstalled, and nothing important lost.

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Uninstalling Apps Leaves Files Behind - How to Remove App Leftovers