How to Check Disk Usage on Mac

Every Mac ships with a fixed amount of internal SSD storage — typically 256 GB, 512 GB, 1 TB, or 2 TB. macOS formats this drive using APFS (Apple File System), which creates flexible volumes that share the underlying physical space. The main volumes are Macintosh HD (the system volume) and Macintosh HD - Data (user files and applications).

macOS categorizes storage into system files, applications, documents, photos, media, mail, and other categories. Understanding how space is distributed helps identify what consumes the most storage and where cleanup efforts have the greatest impact.

Open the Apple menu in the top-left corner and select About This Mac. On macOS Ventura and later, click More Info, then scroll down to Storage. On older versions, click the Storage tab directly. The panel displays a colored bar representing each storage category.

The Manage Storage button opens a detailed view with recommendations: Store in iCloud, Optimize Storage, Empty Trash Automatically, and Reduce Clutter. Each recommendation shows how much space it can recover. The sidebar lists applications, documents, mail, and other categories sorted by size.

macOS Settings shows a snapshot of disk usage at a single point in time. The panel does not update in real time and requires manual navigation each time you want to check available space.

macOS marks certain files as purgeable when they can be regenerated or re-downloaded. Browser caches, font caches, and system caches are purgeable because macOS can rebuild them. iCloud Drive files with the "Optimize Mac Storage" setting enabled are purgeable because the originals exist in the cloud.

Time Machine creates local snapshots on the internal drive before each backup. These snapshots allow you to restore files even when the Time Machine drive is disconnected. macOS automatically purges old snapshots when disk space runs low.

Purgeable space explains why Finder and macOS Settings sometimes report different available space values. Finder shows strictly available space, while the Storage panel may combine available and purgeable totals depending on the macOS version.

Xcode alone can consume 30-50 GB when including simulators, derived data, and platform support files. Games downloaded through Steam or the App Store routinely occupy 20-100 GB each. These applications are the largest single consumers of storage on most developer and gaming Macs.

Cached media from Music, Podcasts, and TV accumulates over time. Podcast episodes set to auto-download can consume gigabytes without the user noticing. Streaming services cache content for offline playback, and these caches persist until manually cleared or the system purges them under storage pressure.

System log files in /var/log and application logs in ~/Library/Logs can grow to several gigabytes on Macs that have not been restarted in weeks. iOS backups stored through Finder (previously iTunes) can consume 10-50 GB per device and are not automatically deleted when you switch to iCloud backups.

MoniThor shows disk usage as a percentage and absolute value in the menu bar, updating in real time as files are created, downloaded, or deleted. The compact panel displays used space, total capacity, and available space in a single view without navigating to System Settings.

Purgeable space appears as a separate value, helping you understand how much storage macOS can reclaim automatically versus how much is genuinely occupied. Real-time read and write speeds show current disk throughput, useful for monitoring large file transfers, backups, or compilation workloads.

MoniThor lists the top 5 storage categories with their folder sizes, identifying the largest consumers of disk space at a glance. External volumes are auto-detected when connected, displaying their usage alongside the internal drive without manual configuration.

Emptying the Trash is the simplest way to recover space. macOS does not permanently delete files when you move them to Trash — they remain on disk until you right-click the Trash icon and select Empty Trash. Enable "Remove items from the Trash after 30 days" in Storage settings for automatic cleanup.

Unused applications can be removed by dragging them from the Applications folder to the Trash. For a more thorough removal, check ~/Library/Application Support and ~/Library/Caches for leftover data from uninstalled apps. Some applications leave hundreds of megabytes in support files after deletion.

Browser caches in Safari, Chrome, and Firefox accumulate gigabytes over time. Clear them through each browser's settings. System caches in ~/Library/Caches can be safely deleted — macOS regenerates them as needed.

iCloud Drive with Optimize Mac Storage enabled keeps only recently accessed files on the local drive and offloads the rest to the cloud. This is particularly effective for large photo libraries, where macOS stores optimized thumbnails locally and full-resolution originals in iCloud.