A native macOS utility
Deadweight
Edition 1.0 · MMXXVI
Find duplicates · Map your disk
✦ Native, local-only, and quietly free.

The gigabytes
your Mac is hiding.

A native SwiftUI app built for everyday humans who need disk space back immediately, but want byte-for-byte certainty that they aren't trashing their original files.

↓ Download for macOS Read how it verifies files →

Requires Apple Silicon · macOS 14 Sonoma or later

Space Doctor: your disk, drawn as a skyline each tower is a junk category · hover to inspect
DerivedData 33 GB.ARW raw shootsnode_modules.mov exportsiOS backups.wav stems.dmg installers~/Library/CachesOld DownloadsTrash 84 GB DerivedData 33 GB.ARW raw shootsnode_modules.mov exportsiOS backups.wav stems.dmg installers~/Library/CachesOld DownloadsTrash 84 GB

A functional desktop utility. No wrapper.

Written in Swift, for macOS, and nothing else. Scanning runs off the main thread, so the window keeps answering you while it works through a few hundred thousand files. Here is the whole of Space Doctor, labelled.

The Space Doctor window: the Space and Duplicates tabs and scan buttons down the left, a disk usage bar across the top, the skyline map of the disk, a bar reading 62.07 GB ready to reclaim, and a row of cleanup insight cards
Space DoctorHover any part of the window.
Space Doctor 01/06swipe →

The clutter you can’t see is the clutter that costs you.

Two kinds of weight pile up on a Mac: the build junk you never see, and the media that quietly copies itself. Deadweight goes after both.

i.

Everyday Users

The Downloads folder that became a junk drawer. Years of .dmg installers you opened once. The same vacation photos imported three times, an old iPhone backup, that 40 MB PDF saved in five places. Deadweight does the boring detective work, finding exact matches no matter what they’re named or where they’re hiding.

// the classic: a Downloads folder quietly holding 90+ GB
ii.

Developers

Xcode DerivedData. Simulator runtimes you forgot you installed. Archives from a version you shipped two years ago. A node_modules in every repo you ever cloned. Deadweight sorts them into categories you can clear without touching your projects or your configs. All of it rebuilds itself the next time you hit build.

// often 20–50 GB hiding in ~/Library/Developer
iii.

Photographers & Creators

You imported the same card twice. The raw .ARW files live in the shoot folder and the edit folder. There are six bounce-downs of a mix you kept re-exporting. Deadweight puts the identical copies side by side, and moves the spares to the Trash while the one you are working from stays exactly where it is.

// "track_4.wav: 11 identical copies found"

Three passes. Nothing deleted until the bytes match.

Most baseline search apps perform naive checks matching on filename and global size, which is a great way to lose work files that happen to share parameters. Deadweight demands proof first.

VERIFICATION
PIPELINE
size
→ sampled fingerprint
→ byte-for-byte compare
SIZE

Bucket by exact byte size

Every file is grouped by size. Anything with a unique size cannot possibly have a duplicate, so it’s dropped immediately. The cheapest filter runs first.

cost: near-zero · reads nothing
SAMPLED FINGERPRINT

Fingerprint the head, tail & interior

Surviving buckets get a fast fingerprint: the first 16 KB, the last 16 KB, and a few interior samples, hashed in parallel across your cores. Catches the obvious mismatches, including files that share a head and tail but differ in the middle, without reading whole files.

cost: light · partial reads
FULL CONTENT

Confirm with a streamed byte-for-byte compare

Only files that already collided get the expensive treatment: the survivors are streamed side by side in 1 MiB chunks and the actual bytes are compared, bailing at the first chunk that differs. The verdict comes from the bytes themselves, not from a hash of them, so there is no collision to gamble on. A match is a fact, not a statistical bet. (A file small enough that the head and tail reads already covered every byte of it is settled right there, because there is nothing left to read.)

cost: heavy · runs on a tiny set
The expensive work only ever touches files that already look identical, so it stays fast on enormous libraries while remaining safe enough to trust with your originals. Two files that are really one file under two names (a hardlink) are recognised before anything is read, and never offered to you as a duplicate or counted as space you can get back. Removals go to the Trash, recoverable, never a silent permanent wipe.
Privacy by architecture

Nothing
leaves your Mac.

A disk-cleaning app sees everything: your filenames, your folders, your life. Deadweight’s answer is not a privacy policy you have to believe. It is the absence of any way to leak it. There is no backend, no account, no embedded analytics. The app makes no network connections at all.

  • No network code.Watch it in Little Snitch. There is nothing to see, because there is nothing to send.
  • No account, ever.Nothing to sign up for. Download, open, scan.
  • Your results are never written down.No paths, no filenames, no lists. Six UI preferences get saved, and the Privacy Policy names all six. Everything else dies with the process.
0
bytes that ever leave your machine
The price
Free.

The whole app. No trial, no “pro” tier, no upsell, no catch.
Built it for myself, releasing it for you.

↓ Download Deadweight 1.0

macOS will ask you to confirm the first time you open it, because Deadweight is given away directly rather than through the App Store. One time, about two minutes. How to open it, with video →

If Deadweight pulled its weight, you can . Entirely optional, deeply appreciated.

The questions a careful person asks first.

Is it safe to let it delete my files?

Yes, by design. Removals move files to the Trash, where they stay recoverable. Two actions are permanent, and both sit behind an explicit confirmation that says so: emptying the Trash from inside the app, and deleting a Time Machine local snapshot. Everything else can be restored from the Trash. And a “duplicate” is only ever shown after a full-content byte-for-byte comparison, so it really is byte-for-byte identical, not just same-name-same-size.

Why didn’t it find a duplicate I know I have?

Most likely one of two defaults. Deadweight only considers files of 1 MB or larger, so small duplicates are ignored until you lower the minimum size in the app. It also skips dependency folders like node_modules, .git and DerivedData, because copies in there are churn rather than clutter and walking them is slow. Both are adjustable: drop the minimum size from the toolbar, and tick the dependencies box when you scan a single folder.

Will the space it reports actually come back?

Usually, with one honest caveat. macOS can store two identical files as a single shared copy on disk (APFS clones, which is what Finder’s Duplicate and cp -c create), so trashing one of them may free less than the figure shown. Hardlinks are detected and never counted as reclaimable at all. The number is an estimate, and it is deliberately conservative about what it promises. macOS can also take up to a day to hand back space held by local snapshots.

Why the “cannot be verified” warning?

Because Deadweight is distributed directly rather than through the App Store, and I’m an independent developer who hasn’t paid for Apple’s notarization service. The warning is macOS being cautious about any outside app, not a sign of trouble. Follow the install guide once and it never appears again.

Why is it free?

Because I built it for myself and it costs me nothing to share. There is no account, no analytics, and no network code, so there is no business model hiding behind the price. You can confirm the network part yourself with a tool like Little Snitch. If you would like to support it, there is an optional tip jar.

Why isn’t it open source?

It’s closed-source freeware, common for indie Mac utilities. You’re welcome to use it free of charge; I’ve simply chosen to keep the source private. The privacy guarantees don’t depend on reading the code: they come from the app having no network behaviour at all, which is observable from the outside.

What are the requirements?

An Apple Silicon Mac (M1 or later) running macOS 14 (Sonoma) or later, including macOS 26 (Tahoe). It’s a native Apple Silicon build and does not run on Intel Macs. Full Disk Access is optional but lets it read the Trash and system-cache categories.