Atlas Storage Analyzer

See what's eating your disk — at a glance. A fast, native macOS disk usage analyzer that turns a folder or volume into a sortable tree and an interactive treemap, so you can find the space hogs and reclaim gigabytes in seconds.

Atlas Storage Analyzer is a free, open-source disk space analyzer for macOS — a native WinDirStat, DaisyDisk, and GrandPerspective alternative for Apple Silicon and Intel Macs. If you're wondering what is using my disk space on Mac and want to free up storage, it scans folders and volumes and visualizes the results as a sortable folder tree, a proportional treemap, file-type statistics, and a list of the largest files — so you can find the space hogs and reclaim gigabytes in seconds.

Atlas Storage Analyzer is free on GitHub and free on the Mac App Store, for users who prefer Store installation and updates. The public Support page explains how to report issues, and the Privacy Policy describes the app's local-only data handling.

Highlights

🗺️ Folder tree + interactive treemap, side by side

Every scan gives you two synchronized views: a folder tree sorted by size and a proportional treemap where the biggest blocks are the biggest consumers. Click a block to inspect it — name, full path, item kind, scan-time dates, and size — and jump straight to it.

⚡ Live progress, and stop whenever you want

Scanning is fully async and streams progress as it runs: current path, file and folder counts, and bytes scanned so far. Big volumes (hundreds of thousands of files) stay responsive, and a single click cancels — partial results stay visible.

📊 Breakdown by file type and largest files

Two dedicated tabs answer the questions that matter: which kinds of files take up the most room? and what are the single biggest files on disk? — each with counts, sizes, and full paths.

File types	Largest files

🧩 Exact duplicate review

After a scan completes, run an opt-in duplicate analysis to find byte-identical regular files. Atlas Storage Analyzer narrows candidates by current logical length, samples file edges, hashes surviving content with bounded buffers, and confirms matches byte for byte before showing them. Analysis can be cancelled, hardlinked paths are shown as linked paths rather than reclaimable copies, and known cloud-only placeholders are skipped instead of downloaded. Duplicate entries can be selected for Quick Look, Finder reveal, and the existing cleanup basket, but Atlas Storage Analyzer never auto-selects a copy for cleanup.

🔎 Preview, reveal, or move to Trash — safely

Found something to inspect? Preview the selected item with Quick Look, reveal it in Finder, move an eligible item to the Trash after a confirmation, or collect multiple scanned items in the cleanup basket for a final review. Broad or sensitive containers are blocked from in-app cleanup with an explanation. Files are never permanently deleted — approved cleanup items go to the macOS Trash, and partial failures identify the item that could not be moved.

📦 Archive instead of delete

Short on space but not ready to let go? Move or copy the reviewed cleanup basket to an external or network volume instead of the Trash. The review names the operation and the destination, and reports the expected locally reclaimed size — zero for a copy, since a copy frees nothing. Nothing at the destination is ever replaced: an item whose name already exists there is blocked with a reason rather than overwritten or auto-renamed. A move across volumes copies first, verifies the copy, and only then removes the original, so a failed or cancelled transfer always leaves the source in place.

⚙️ Configurable scanning

Fine-tune what gets counted: scan inside .app bundles (or treat them as single items), include hidden files, and follow symbolic links. By default sizes use shared-aware allocated measurement: repeated hardlink identities count once, and verified full-clone data counts once on capable volumes. Independently allocated non-data storage and divergent clone extents remain per identity. You can instead choose allocated size per path or logical file length. See Storage measurement semantics for capability coverage and scope. Preferences and manageable recent scan locations are remembered between runs.

Features

• Select and scan any folder or volume with live progress reporting, and cancel a running scan at any time.
• Browse results as a folder tree sorted by size, or as an interactive treemap.
• Inspect selected file and folder metadata captured during the scan, including item kind and available created or modified dates.
• Preview the selected item with Quick Look using the toolbar or its Actions menu, and use Space or Command-I shortcuts for inspection.
• See storage broken down by file type and a list of the largest files.
• Run opt-in exact duplicate analysis after a scan completes. Duplicate analysis reads local file contents only when candidates survive metadata and sample checks, can be cancelled, skips known cloud-only placeholders, shows hardlinks as linked paths, and lets duplicate entries flow through the same Quick Look, Finder reveal, and cleanup-basket review commands as other scanned items.
• Search and filter scanned items by name or path, and press Command-F to jump to the search box.
• Narrow a completed scan with advanced filters covering size, creation, modification and last-access dates, file extension, file category, and shared-storage status. Criteria combine with AND, and filtering never rescans.
• Set each date bound to a fixed date or to a span before the moment the filter runs, such as 18 months ago. A relative bound is stored as the span, so a saved preset keeps meaning the same span instead of drifting as time passes. The panel shows the date each span resolved to.
• Apply built-in filter presets, or save, rename, delete, and update your own. Presets persist between runs, and the panel shows which preset the current criteria match and whether they have been edited since.
• See the number of matching files, their total matched size, and how many files were excluded because a required date was unknown.
• Export the current result as CSV or JSON to a location you choose. Exporting with a filter active writes the matched files only. JSON preserves paths exactly and carries the scan's unreadable-path list; CSV is written for spreadsheets, with a UTF-8 byte order mark and leading formula characters neutralized so no cell executes on open. A cancelled or failed export never leaves a partial file behind.
• Optionally record completed scans to a local history, so a later release can show what grew or shrank between two points in time. Recording is off until you turn it on, snapshots stay on your Mac and never include file contents, and the store is capped by snapshot count and total size. You can delete a single recorded scan or clear the whole history at any time.
• Reveal items in Finder, move one eligible item to Trash, or review a multi-item cleanup basket before moving approved items to Trash. Broad or sensitive containers are blocked from in-app cleanup with an explanation.
• Move or copy the reviewed cleanup basket to another volume instead of the Trash. Destination free space, read-only destinations, and moves into an item's own subtree are checked before the review, colliding names are blocked rather than overwritten, and a cross-volume move only removes the original after the copy is verified.
• Inspect files and folders that couldn't be scanned, and copy their paths to the clipboard.
• Get access guidance when macOS-protected locations make a scan appear incomplete: a shortcut to Privacy & Security with manual fallback instructions in the GitHub build, selection guidance in the sandboxed Mac App Store build, and a rescan action in both.
• Configurable scanning: hidden files, symbolic links, .app package expansion, and logical, per-path allocated, or shared-aware allocated size measurement.
• Remembers your scanner preferences and recent scan locations between runs, with controls to remove individual entries or clear the list.
• Modern, native-feeling UI that follows the system light/dark appearance, with a responsive treemap and a live scan-progress overlay.

Completed-result screenshots above show Atlas Storage Analyzer analyzing a prepared demo folder of photos, caches, archives, design assets, and video projects, so the breakdown reflects the kind of library a real user scans.

Branding artwork lives under src/MacStorageAtlas.App/Assets/: app.ico (window icon), icon.png (1024×1024 master), and MacStorageAtlas.icns for macOS app bundling.

How it compares

Looking for a free DaisyDisk alternative or a WinDirStat for Mac? Atlas Storage Analyzer focuses on the essentials — a fast scan, a treemap, and safe cleanup — without a subscription or a price tag.

Capability	Atlas Storage Analyzer	DaisyDisk	GrandPerspective	WinDirStat
Platform	macOS (Apple Silicon + Intel)	macOS (Apple Silicon + Intel)	macOS (Apple Silicon + Intel)	Windows
Distribution	Free, MIT-licensed open source; free on GitHub and the Mac App Store	$9.99 one-time commercial license	Free GPL build; $2.99 App Store build	Free, GPLv2 open source
Main analysis views	Folder tree, rectangular treemap, file-type statistics	Sunburst disk map and sidebar list	Rectangular treemap	Directory/file lists, treemap, and extension statistics
File-size measurement	Logical length, allocated blocks per path, or shared-aware allocated blocks; hardlinks and verified full-clone data count once where capability coverage permits	Physical size; hardlinks and full APFS clones are counted once	Logical, physical, or file-count sizing; hardlinks counted once per view	Logical or physical sizing with hardlink deduplication

Storage-measurement note: these products do not use one interchangeable definition of “real size.” Atlas Storage Analyzer handles sparse files and local cloud placeholders and, by default, counts hardlinks once plus verified full-clone data once on capable volumes. It does not deduplicate divergent clone extents and does not claim unique physical or reclaimable storage. The optional per-path mode counts every visited path. DaisyDisk documents full APFS-clone detection on macOS 14 Sonoma and later.

Comparison last verified against the linked first-party sources: 2026-08-27. Prices and capabilities can change; follow the links for current product details.

Prerequisites

• macOS
• .NET 10 SDK
• Avalonia templates are not required to build or run; all dependencies are restored from NuGet.

Build

dotnet restore
dotnet build --no-restore

Test

dotnet test --no-build

Run

dotnet run --project src/MacStorageAtlas.App

Download options

• GitHub release: signed and notarized DMGs remain available for free from GitHub Releases.
• Mac App Store edition: a free App Store download for users who prefer Store installation and updates.

Package

Run the packaging script from the repository root. It publishes a self-contained Release build, wraps it in a AtlasStorageAnalyzer.app bundle (with the .icns app icon), and creates a DMG with a drag-to-Applications shortcut.

./build-dmg.sh            # Apple Silicon (default) → AtlasStorageAnalyzer.dmg
./build-dmg.sh arm64      # Apple Silicon (osx-arm64)
./build-dmg.sh x64        # Intel (osx-x64)
./build-dmg.sh both       # both architectures, one DMG each

When building both, the DMGs are named per architecture (AtlasStorageAnalyzer-osx-arm64.dmg and AtlasStorageAnalyzer-osx-x64.dmg). Each build is self-contained and does not run under Rosetta on the other architecture — pick the DMG that matches the target Mac.

The default packaging commands produce unsigned development DMGs. Official public release artifacts use the explicit local Developer ID path, which signs the app with the runtime entitlements required by CoreCLR, notarizes and staples the DMG, verifies the result, and writes SHA-256 checksum files:

./build-dmg.sh release both 1.2.3 \
  "Developer ID Application: Example Company (TEAMID)" \
  "MacStorageAtlas-notary"

Release DMGs are named AtlasStorageAnalyzer-<version>-<runtime>.dmg. See Packaging Atlas Storage Analyzer for macOS for certificate, notary profile, verification, and GitHub Release upload steps.

Mac App Store packages use Apple Distribution and Mac Installer Distribution certificates and produce uploadable .pkg files:

./build-dmg.sh appstore both 1.2.3 \
  "Apple Distribution: Lachmann Thiem Software GbR (2G3HGCLNFN)" \
  "3rd Party Mac Developer Installer: Lachmann Thiem Software GbR (2G3HGCLNFN)"

Access to protected locations

macOS can block an app from reading a location, and the remedy differs per distribution channel. In both cases Atlas Storage Analyzer shows guidance that the result may be incomplete, keeps the detailed errors visible, and offers a rescan. Inaccessible paths are not purgeable space, free space, or files that Atlas Storage Analyzer says are safe to delete.

The GitHub Release build is not sandboxed. macOS can block protected locations such as some Mail, Messages, Safari, Time Machine, and administrative data. Grant access manually in System Settings > Privacy & Security > Full Disk Access, add or enable Atlas Storage Analyzer, restart the app if macOS asks, then rescan the same location.

The Mac App Store build runs in the macOS App Sandbox and can only read folders and volumes you select in the open panel. Full Disk Access does not change that, so the guidance asks you to select the missing location and rescan instead, and the Full Disk Access action is not shown.

Trash and Finder reveal use macOS file and workspace APIs directly, so both work in the sandboxed build without Apple event automation.

Project structure

src/
  MacStorageAtlas.App              Avalonia UI and MVVM shell
  MacStorageAtlas.Core             disk scanning and domain logic, grouped by domain folder
  MacStorageAtlas.Rendering        treemap layout logic
  MacStorageAtlas.Platform.Mac     macOS-specific integrations (reveal, trash, dock icon, access guidance)

tests/
  MacStorageAtlas.Core.Tests       Core NUnit tests mirroring Core domain folders
  MacStorageAtlas.Rendering.Tests  Rendering NUnit tests
  MacStorageAtlas.Platform.Mac.Tests macOS integration NUnit tests
  MacStorageAtlas.App.Tests        App and ViewModel NUnit tests
  MacStorageAtlas.Benchmarks.Tests benchmark tooling NUnit tests

tools/
  MacStorageAtlas.Benchmarks       developer scan benchmark command

Documentation

• Public support page: docs/support.html
• Product backlog and feature specifications: docs/FEATURES.md
• Market-driven implementation roadmap: docs/IMPLEMENTATION_ROADMAP.md
• Storage measurement semantics and verification: docs/STORAGE_MEASUREMENT.md
• Troubleshooting: docs/TROUBLESHOOTING.md
• Scan benchmark commands and representative results: docs/SCAN_BENCHMARKS.md
• OpenSpec feature workflow: docs/OPENSPEC_WORKFLOW.md
• macOS packaging and distribution: docs/PACKAGING.md

License

Released under the MIT License.

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