Dragging an app to the Trash removes the app itself. It does not necessarily remove the files the app created while you used it. Those files stay in your user Library, usually small individually, and can add up after you have tried and removed many apps.
Where an app keeps its data
Most of it lives in the hidden Library folder in your home folder. In Finder, hold Option and open the Go menu to reveal Library. The common places are:
- ~/Library/Application Support holds the app’s own data: databases, downloaded content, plug-ins, sometimes licence files.
- ~/Library/Preferences holds settings as
.plistfiles, named after the app’s bundle identifier, for examplecom.company.AppName.plist. - ~/Library/Containers and ~/Library/Group Containers hold the data of sandboxed apps, including most apps from the Mac App Store.
- ~/Library/Caches holds temporary data the app can rebuild. The guide to safe deletions in Library Caches covers it in detail.
- ~/Library/LaunchAgents holds small files that start helper processes at login. A leftover launch agent can try to start a program that no longer exists.
- ~/Library/Logs, Saved Application State and HTTPStorages hold logs, window state and web session data.
Some apps also install files in the system-wide /Library folder, which usually needs an administrator password to change.
Matching a folder to an app
Folder names are not always the app’s name. Many use the bundle identifier, a reverse-domain string. To find it, right-click the app in Finder, choose Show Package Contents, open Contents/Info.plist and look for CFBundleIdentifier. Searching your Library for that string finds most of the app’s files.
The name alone can mislead. Two apps from the same company may share a folder, and a folder named after a company may serve several of its products. Leave a shared folder alone while any app that uses it is still installed.
What is worth removing, and what is not
- Usually safe once the app is gone: caches, logs, saved application state, and the preferences of an app you do not plan to reinstall.
- Think first: Application Support and Containers. They can hold your own work, such as libraries, projects or notes, that the app stored for you. If you might reinstall, or you have not exported your data, keep them.
- Do not touch: anything belonging to macOS itself, and anything you cannot match to an app with confidence.
A running app rewrites some of these files, so quit an app before you remove its data. Once you empty the Trash the files are gone, so read about how the Trash behaves first.
How the app approaches leftovers
The app is in pre-alpha, and this describes the design rather than a finished feature. The Leftovers section is meant to group files by the app they appear to belong to, separate the ones it is confident about from the ones it is not, and explain each item before you choose. In the current build, the Balanced preselection level includes confirmed leftovers and only the Everything level includes possible ones, and every item still needs your review before anything moves to the Trash. Cleanup itself is not built yet, so nothing in the app removes files today.