My favorite kind of apps are those created by developers to scratch their own itch^[1], who then realize, Hey! This could be useful for others!

Hyperspace is that kind of app. John Siracusa—writer, critic, podcaster, and file system aficionado—initially created Hyperspace to validate his intuition that it should be possible to recover space on his ever-growing disk without deleting files, by using clones, a well-known but underutilized feature of today’s macOS file system:

If I could find files that had the same content but were not clones of each other, I could convert them into clones that all shared a single instance of the data on disk. I took an afternoon to whip up a Perl script (that called out to a command-line tool written in C and another written in Swift) to run against my disk to see how much space I might be able to save by doing this. It turned out to be a lot: dozens of gigabytes.

(In his inimitable style, Siracusa’s announcement is long, detailed, and peppered with hyperlinks. The documentation is likewise quite extensive, including an explanation of exactly how the app works. Also: of course Siracusa released a file systems-based app 🛎️.)

The result of his experiment is a thoughtfully designed app that elegantly solves the “duplicate files” issue many of us face, while preserving important file hierarchies—an underrated consideration without which files could be “lost” for apps (like Apple Photos) that rely on the file system for organization (as do many people, like me). The app also offers just enough options to exert control over which files and folders are impacted by the reclamation process.

(One welcome option: You can specify a folder as the “source,” ensuring that files in that location are never modified, useful if you have, say, a main photos library and several incremental backups you’re pruning.)

Over the years, as my storage space grew, unbounded, I’ve wondered whether an app like this was possible. It’s become especially problematic as I accumulate many copies of copies of backups—the same files, across different folders and drives. I’ve tried many apps that find and delete duplicate files, but the results were always unsatisfying: It was difficult to mark which files were the “original”, which duplicates should be deleted, and after dispatching those dupes, files were no longer where they should be. I was always left with a sense of unease—it felt like data loss, even though technically, it wasn’t.

Using Hyperspace, on the other hand, is deeply satisfying. In the end, everything on disk looks exactly the same, all my files are just where they were before, but now there’s more space on my drive. It’s indistinguishable from magic.

Hyperspace is, to use Siracusa’s own words, “an incredibly dangerous app.” Its clever conceit manipulates your files in ways which could end in catastrophic data loss. I recommend running this app (really, any duplicate removal app) on a clone of your drive, just in case. (I suggest Carbon Copy Cloner, my cloning app of choice for 20 years, to make that copy.)

That said, if I trust anyone to be hyperaware of potential data loss, it’s John Siracusa. His love of and experience with file systems, his four decades of Mac expertise, and his, shall we say, obsessive nature when it comes to backups (data and otherwise), are all reflected in the careful construction of his app. He has a clear understanding of the complexities and potential consequences of using the clone technique, and takes several precautions in the app to protect you from losing data during what is an undeniably delicate process. He is extremely circumspect about which files the app acts on; the app won’t even touch system or cloud-based files, which he deemed too dangerous for his initial release, and the app will stop at the slightest sign of trouble (with actionable error messages) rather than proceed down a potentially unsafe path. That he ran it against his own precious Photos library was itself a compelling convincer.

The app is free to download and scan your drive to identify files to be reclaimed, with a $10 In-App Purchase to complete the reclamation and free up space.

(Siracusa could have easily justified charging based on the amount of space recovered. Even his Lifetime Unlock ($50) is undervalued.)

Hyperspace is Siracusa’s most Siracusa-y app yet. I think it’s a winner.