# How See Your Disk cleans: methods and safety levels

_Updated 2026-10-15_

A cleaner has to earn trust, so this page says plainly what See Your Disk removes, how it decides, and what it will never touch. If you want the background first, start with [what System Data is](/guides/what-is-system-data-on-mac/).


## The principle: known locations, not guesses

- The app works from a **fixed list of locations** that are known to hold regenerable data. It does not guess, and it does not use a model to decide.
- Every location has a **safety level**: Safe, Review or Protected.
- **Nothing is removed until you confirm.** The confirmation shows how many items and how many gigabytes.
- The app reads **file names and sizes only**, never the contents of your files, and nothing leaves your Mac.


## The three safety levels

| Level | What it means | Examples | How it is removed |
|---|---|---|---|
| Safe | Apps or tools rebuild it on their own | Per-app caches in ~/Library/Caches, logs, Xcode DerivedData and device support, simulator caches, the npm cache, Chrome updater downloads, items already in the Trash | Deleted for good, so the space is free at once |
| Review | Often useful, or costly to get back | Xcode Archives, simulator devices, the Gradle cache, tool caches such as AI models in ~/.cache, downloaded aerial wallpapers, and your own files over 500 MB | Moved to the Trash, so you can put it back |
| Protected | Shown, but never removable by the app | Docker's virtual disk image | Not removed. The app explains how to free the space safely instead |


## What Auto clean does

Auto clean ticks **only the Safe items**, shows you the list and the total, and waits for your confirmation. You can also open any block on the map, see what can be cleaned inside it, tick or untick items and clean just those. Selected items are striped on the map so you can see what will go before you confirm.


## What it never touches

- System files, swap, and the snapshots macOS keeps for updates.
- Anything outside the Home folder you granted to the app.
- Your documents, photos and other personal files. Large files of yours are listed as Review, never selected for you.
- Locations that need administrator rights. The app does not ask for your password and does not run `sudo`.


## Why some big things are protected or marked Review

Docker keeps all its data in one large disk image. Deleting that file would destroy every container and volume, so the app shows it but leaves it alone and points you to Docker's own cleanup. AI model caches such as Hugging Face can be many gigabytes, but they cost real time to download again, so they are Review rather than Safe.


## How the map measures size

- It uses the space files actually occupy on disk (allocated size), which is what Storage settings is about.
- It does not follow symbolic links and does not cross into other volumes, so nothing is counted twice.
- Many tiny items are grouped into one block labelled Small items, with the largest of them listed on the right.
- The result can differ from Finder's Get Info and from Storage settings, because of APFS clones, snapshots and purgeable space.


## Check the rules yourself

See Your Disk is open source under the MIT license. The list of locations and their levels is in [Cleanup.swift](https://github.com/bikmeev/see-your-disk/blob/main/SeeYourDisk/Core/Cleanup.swift), and you are welcome to suggest new rules or report a wrong one on [GitHub](https://github.com/bikmeev/see-your-disk).

Get See Your Disk: [Mac App Store](https://apps.apple.com/us/app/clean-systemdata-seeyourdisk/id6817565741) · [GitHub](https://github.com/bikmeev/see-your-disk)

## Frequently asked questions

**Does See Your Disk use AI to decide what to delete?**
No. It uses a fixed, readable list of known locations. There is no guessing and no model deciding what to remove.

**Can Auto clean delete my documents or photos?**
No. Auto clean only selects items marked Safe, such as caches and logs. Your own files are never selected automatically, and large files of yours are marked Review.

**Can I undo a cleaning?**
Safe items are things apps recreate on their own, so there is nothing to restore. Anything that is not clearly safe goes to the Trash first, so you can put it back.

**Can I read the rules?**
Yes. The app is open source and the rules are in one file, Cleanup.swift, in the GitHub repository.

## Related guides

- [What is System Data on Mac, and why is it so big?](https://seeyourdisk.com/guides/what-is-system-data-on-mac/)
- [How to clear System Data on Mac safely](https://seeyourdisk.com/guides/how-to-clear-system-data-on-mac/)