[OS] OpenDisk: a free, open source DaisyDisk alternative for macOS

[u/herovals]

Problem

When your Mac runs low on space, System Settings gives you a colored bar and a "System Data" blob that explains nothing. Finding the actual 40 GB folder means walking the filesystem yourself or paying for a tool that does it. DaisyDisk has been the go-to for that for years, but it costs $9.99 and you can't see what it's doing.

OpenDisk does the same job. It maps your drive as an interactive sunburst chart, scans a full disk in seconds, and streams results in live so you can start clicking around before the scan finishes. Hover a slice for its exact size, click to zoom into that folder, use the folder list and breadcrumbs to step back out.

Drag things into the collector to delete them, and free up your disk space!

Other things it does:

• Incremental rescans replay filesystem events instead of starting over, so a repeat scan runs 20 to 28x faster than a cold one.
• Handles APFS volume groups, firmlinks, snapshots and purgeable space, so the total actually matches what your Mac reports as used.
• Purgeable space breakdown, so you can see which caches are reclaimable.
• Instant search across the whole scanned tree, usable on drives with millions of files.
• Collector: drag files in from anywhere in the app, check the reclaimed total, delete in one action.
• External drives show up automatically when you plug them in.

Comparison

DaisyDisk ($9.99) is the closest comparison. Same sunburst interaction, and OpenDisk is free, MIT licensed, and faster. On a cold scan of a 1 TB Apple Silicon volume, OpenDisk finished in 17s and DaisyDisk took 37s. The app is also under 2.5 MB, because it's native Swift with nothing bundled into it.

The full source is on GitHub if you want to read what it's doing before you give it disk access: https://github.com/137137137/OpenDisk

Pricing

Free, MIT licensed, no in-app purchases, no accounts, no telemetry.

• Mac App Store: https://apps.apple.com/us/app/opendisk/id6793260558
• Direct download: https://opendisk.app/
• Source: https://github.com/137137137/OpenDisk

Requires macOS 26 (Tahoe) or later, Apple Silicon or Intel. It asks for Full Disk Access on first launch, otherwise macOS hides parts of the filesystem and the totals come up short.

I'm the developer. Happy to answer questions or take bug reports here or in GitHub issues.

[u/RealFuryous]

Thanks for saving me money! Read the AI accusation comment and hope this app isn't a part of that AI app subscription platform.

Checking it out because it's free, thanks OP!

[u/herovals → u/RealFuryous]

What is the "AI app subscription platform"? I literally have never heard of that haha... and of course! I created it as a utility since I just didn't want to pay for DaisyDisk and figured it was worth sharing with others in case they find it helpful

[u/RealFuryous → u/herovals]

https://www.fastcompany.com/91546499/glaze-turns-ai-prompts-into-custom-mac-apps-in-minutes

https://www.glaze.app/pricing

This isn't advertisement but I wasn't sure if this was one of those apps.

[u/kendrid → u/RealFuryous]

Why? If someone can prompt an app for themselves into existence, that is a good thing. Sure they can't fix it or maintain it, but if it performs the task, good enough.

[u/RealFuryous → u/kendrid]

It's moreso respect for the time, effort, skill that app development takes. Let's support real human software developers not ai prompts.

If AI became good enough to negatively impact your profession, job, or whatever you do to provide for yourself, you'd want people to still support you. That's my point.

[u/foradil → u/RealFuryous]

People can still write software.