AppCleaner

Dragging an app to the Trash leaves most of it on disk: preference plists, caches, launch agents, a folder in Application Support, sometimes a login item that keeps failing quietly. AppCleaner collects those, shows you the list, and removes the set. Its best feature is SmartDelete, a background watcher that notices you trashed something and offers to finish the job, so you stop having to remember the tool exists at the moment you need it.

It has been free since 2007, with no paid tier, no store page and no upsell — only a donate link. The catch arrives in another form: development is quiet, and right now the newest build on the download page covers Mojave through macOS 26, with nothing listed for macOS 27. Check the page before you count on it.

Because it matches files by name and bundle identifier it is not magic. It can miss an oddly named leftover, and it will occasionally offer up something you want to keep, so read the list rather than clicking through. It also does none of the other things cleaner suites advertise — no cache sweeping, no browser extensions, no "system junk". It uninstalls apps, which is the only part of a paid cleaner most people ever used.