DiskManager
GitHub
Free & open source · macOS 14+

Sync and clean up two drives safely

DiskManager compares two drives or folders, shows you exactly what will change, and only then mirrors, prunes or merges them.

Download for Mac Source code

v0.3.0 · Apple Silicon · macOS 14 or later · MIT license
macOS blocks the first launch?

DiskManager sync tab showing a mirror plan between two drives
Features

One app for keeping two storage spaces in shape

Built for anyone juggling external drives: a travel SSD and a home archive, two backups kept in different places, or just two folders that drifted apart.

Sync with a plan you can read

Scanning is read-only. You get the full plan first: what will be added, overwritten or archived, folder by folder.

  • Three modes: Mirror, Difference, Union
  • Browsable diff tree with sizes and counts
  • Storage bars that block a sync that won't fit

Clean up what you don't need

Finds space you can safely reclaim, grouped into categories and subcategories. Nothing is removed until you tick it.

  • Regenerable Final Cut Pro / iMovie render and proxy media (never Original Media)
  • Disk images, .DS_Store, ._ files, Lightroom and Premiere caches
  • Duplicate files and near-identical folders

Ask AI about the results

Open the chat panel and attach the current plan or report. Ask which folders take the most space or which duplicate to keep.

  • Claude or GPT with your own API key
  • Keys live only in the macOS Keychain
  • Advice only: the AI can't touch your files
A→B

Mirror

Bring B up to date with A. Files missing from B are copied, outdated ones overwritten, and files that exist only on B are archived.

B−A

Difference

Lists only what B has and A doesn't, then archives or trashes it after you confirm. Nothing is copied or overwritten.

A⇄B

Union

Fill in both sides. When a file differs, the newer one wins and the older is archived. Anything ambiguous is left alone and listed.

Preview firstNothing changes until you press Start.
Archive, don't deleteReplaced files go to _DiskManager_Archive.
Atomic copiesCancel anytime without half-written files.
Private by designNo account, no tracking. The only network calls come from the AI chat, and only when you use it.
Screenshots

See it in action

The screenshots follow this page's language and theme, just like the app.

Sync tab
Mirror mode: 95 new files and 2 updates to copy to Backup Drive. The 7 items that exist only on B will be archived, and the storage bars show whether everything fits.

Screenshots use demo drives. Click to view full size.

Install

Install and open DiskManager

Takes about a minute. The Gatekeeper step is needed only on first launch.

1

Download and move to Applications

Download the latest DiskManager-x.y.z.zip, double-click it to unzip, then drag DiskManager.app into your Applications folder.

2

Open it past Gatekeeper

DiskManager is code-signed but not notarized by Apple, since notarization requires a paid Apple Developer membership. On first launch, macOS shows a warning like:

Apple could not verify “DiskManager” is free of malware that may harm your Mac or compromise your privacy.

This doesn't mean the app is harmful. It only means Apple hasn't reviewed it. The full source is on GitHub. Pick one of these:

System SettingsmacOS 15 Sequoia and later

  1. Double-click DiskManager, then click Done in the warning.
  2. Open System Settings › Privacy & Security and scroll down to Security.
  3. Next to “DiskManager was blocked…”, click Open Anyway.
  4. Confirm with your password or Touch ID, then click Open Anyway again.

Right-click › OpenmacOS 14 Sonoma

  1. In Finder, Control-click (or right-click) DiskManager in Applications and choose Open.
  2. Click Open in the dialog that appears.

TerminalAny version

Remove the quarantine flag macOS added to the download, then open the app normally:

xattr -dr com.apple.quarantine /Applications/DiskManager.app

After the first launch, DiskManager opens normally with a double-click.

3

Grant Full Disk Access

macOS doesn't let apps request this permission themselves. Open System Settings › Privacy & Security › Full Disk Access, turn on DiskManager (use + to add it if it isn't listed), then relaunch the app.

Without it, macOS asks separately for Desktop, Documents, Downloads and every external or network volume, and protected folders are skipped. The shield in the toolbar shows the current status.

Optional: verify the download

Each release lists the zip's SHA-256 checksum. Compare it with:

shasum -a 256 ~/Downloads/DiskManager-*.zip

Prefer building it yourself? Clone the repository and run make app (requires Xcode command-line tools).