What macOS already includes
Before installing anything, use the tools Apple documents in its storage guidance. System Settings → General → Storage shows the category bar with recommendations: Store in iCloud, Optimize Storage for TV downloads and email attachments, and Empty Trash Automatically. Each category has its own information button: Documents opens Large Files, Downloads and a File Browser sorted by size, and the others list apps, device backups and attachments for deletion.
Add Finder’s Get Info for sizes, the Trash with File → Put Back for undo, Disk Utility for the free-versus-purgeable distinction, and safe mode for a one-off cache clear before an update. For a Mac whose storage is mostly documents, photos and apps, this is the whole toolkit.
Free apps, by the job they do
These descriptions come from each maker’s own page as read on 6 September 2026. We make ClearDisk and have not tested the others side by side, so this is a map of what exists, not a ranking.
- OnyX (Titanium Software): a free multifunction maintenance utility that verifies system files, runs cleaning and maintenance tasks and uninstalls apps, with a separate build for each macOS version. Aimed at people who know which maintenance task they want.
- GrandPerspective: a free, open-source tree map in which each file is a rectangle proportional to its size, so the biggest folders are visible at a glance. Files can be deleted from inside the app, so read a rectangle before clicking it.
- OmniDiskSweeper (The Omni Group): a free list of your files from largest to smallest that lets you Trash or open them. The simplest way to find the ten biggest things on a disk.
- AppCleaner (FreeMacSoft): a free uninstaller that finds the small files an app leaves around the system and deletes them with the app.
- ClearDisk: free, unlimited local scanning with a System Data breakdown labelled Safe, Review or Leave it, a storage map, a largest-files list and Reveal in Finder. Cleanup from inside the app, Trash-first with undo, is a one-time license.
How to stay safe with any cleaner
The category attracts bad actors. In January 2026, researchers documented sponsored search results for “mac cleaner” that led to malware. Download from the maker’s own site or the App Store, check that Gatekeeper accepts the app without a workaround, and be suspicious of any tool that promises a fixed amount of freed space, a faster Mac, or memory cleaning, none of which a file scanner can honestly guarantee.
Prefer tools that move files to the Trash rather than deleting immediately, that show you the path of every item before removal, and that tell you when they lacked permission to read a folder. A cleaner that silently skips protected locations produces a confident total that is wrong.
How to choose
Start free and specific. If Storage settings already explains your number, stop there. If System Data is large and unexplained, use a scanner that opens the Library and shows allocated sizes: GrandPerspective and OmniDiskSweeper for a picture, ClearDisk for the breakdown with labels. If old apps are the problem, an uninstaller does the job. If you want maintenance scripts, OnyX is built for that.
Pay only for the part you will use repeatedly. For most people that is either nothing, or a one-time license for in-app cleanup with a way back. Whatever you pick, the guides on this site work with Finder and Terminal alone, so the free path is always open.
References & further reading
These guides combine the linked official guidance with ClearDisk’s documented behavior. Your files and app settings determine the right next step.