How to Check What’s Taking Up Space on Hard Drive

This guide shows you how to find out which files and folders are eating up your hard drive space on Windows or macOS. You’ll learn built-in methods and a free third-party tool approach, so you can reclaim storage without guesswork.

What You’ll Need

Your computer (Windows 10/11 or macOS Catalina or newer)
Administrator access (to view all system files if needed)
Optional: A free disk space analyzer tool like WinDirStat (Windows) or DaisyDisk (macOS, paid) – but built-in tools work fine for most users

Step-by-Step

Open File Explorer (Windows) or Finder (macOS). On Windows, press Win + E. On macOS, click the Finder icon in the Dock.
Go to “This PC” (Windows) or your main hard drive (macOS). On Windows, click “This PC” in the left sidebar. On macOS, click your hard drive name (usually “Macintosh HD”) under “Locations” in the sidebar.
Check overall usage first. On Windows, you’ll see a bar under each drive showing how full it is. On macOS, press Cmd + I on the drive icon to see total and available space.
Use Windows Storage Settings (fastest built-in method). Go to Settings > System > Storage. Click “Show more categories” to see breakdowns for Apps, Documents, Temporary files, etc. Click any category to see individual items.
Use macOS Storage Management. Click the Apple menu > About This Mac > Storage > Manage. This shows recommendations and a breakdown by category (Photos, Documents, etc.).
For a folder-by-folder view, use a disk space analyzer. Download and install WinDirStat (Windows) or a free alternative like TreeSize Free. On macOS, you can use the built-in “Storage” view or a free tool like GrandPerspective.
Run the analyzer. Launch WinDirStat and select the drive you want to scan. It will take a few minutes. You’ll see a treemap – each rectangle is a file, sized proportionally to its disk usage. Larger rectangles = larger files.
Sort by size. In WinDirStat, click the “Size” column header to sort files from largest to smallest. The list at the top shows the biggest files and folders.
Identify large folders. Expand the folder tree to see which subfolders contain the largest files. Common culprits: Downloads, Documents, Videos, AppData (Windows), Library (macOS).
Check temporary and system files. In Windows Storage Settings, click “Temporary files” to see and delete temp files, recycle bin contents, and Windows Update leftovers. On macOS, use Storage Management’s “Optimize” and “Reduce Clutter” options.
Delete or move large files. Right-click a file and choose “Delete” (or move it to an external drive). For apps, uninstall via Settings > Apps (Windows) or drag from Applications (macOS).
Empty the Recycle Bin/Trash. Right-click the Recycle Bin (Windows) or Trash (macOS) and select “Empty” – deleted files still take up space until then.

Common Mistakes

Deleting system files blindly. Never delete files in C:\Windows or /System – you can break your OS. Stick to your user folders.
Ignoring hidden files. Some large files are hidden. In Windows, enable “Hidden items” in File Explorer’s View tab. On macOS, press Cmd + Shift + . in Finder to show hidden files.
Not emptying the Recycle Bin/Trash. Deleted files remain on disk until you empty it.
Deleting files that are in use. You’ll get an error. Close the program first.
Focusing only on files, not apps. Apps can take gigabytes – check your installed apps list.

Tips

Use the treemap visual. The colored blocks in WinDirStat or GrandPerspective make it obvious which files are huge – look for the biggest rectangles.
Sort by size, not name. Always sort by the “Size” column to see the biggest offenders first.
Move, don’t just delete. If you’re unsure, move large files to an external drive instead of deleting them.
Check your Downloads folder. It’s the #1 place for forgotten large files like installers and videos.
Use Storage Sense (Windows). Enable automatic cleanup of temp files in Settings > System > Storage > Storage Sense.
On macOS, use “Optimize Storage” to automatically remove watched movies and TV shows from Apple TV.

Troubleshooting

If the analyzer crashes or takes too long: Close other programs, run as administrator (right-click > Run as administrator), or scan only specific folders (like your user folder) instead of the whole drive.

If you can’t delete a file because it’s in use: Close the program that’s using it. If it’s a system process, restart your computer and try again immediately after boot.

If you see “Access Denied”: You need administrator rights. Right-click the file, select “Properties” > “Security” and take ownership, or run the deletion command as admin. On macOS, you may need to enter your password.

If the space doesn’t free up after deleting: Empty the Recycle Bin/Trash, restart your computer, and check again. Some files are locked by the system until reboot.

If you can’t find the large file but the drive is still full: Use a tool like WinDirStat to scan the entire drive – it will show all files, including hidden system files. Also check for pagefile.sys and hiberfil.sys (Windows) – these are system files that can be several GB, but don’t delete them manually.

Frequently Asked Questions

Q: What is the fastest way to see what’s taking up space?
A: On Windows, go to Settings > System > Storage – it gives a quick breakdown by category. On macOS, About This Mac > Storage > Manage.

Q: Why does my hard drive show less free space than expected?
A: Hidden system files, the Recycle Bin/Trash, and file system overhead (like NTFS or APFS metadata) consume space. Also, drive manufacturers use decimal (1 GB = 1,000,000,000 bytes) while OS uses binary (1 GB = 1,073,741,824 bytes).

Q: Can I delete the Windows.old folder?
A: Yes, if you’ve upgraded Windows and no longer need to roll back. Use Disk Cleanup (cleanmgr.exe) and select “Previous Windows installations” to remove it safely.

Q: Is it safe to delete files in the Temp folder?
A: Generally yes. Use Disk Cleanup or Storage Sense instead of manually deleting – some temp files may be in use.

Q: How do I find large files on an external drive?
A: Connect the drive, then run WinDirStat (Windows) or GrandPerspective (macOS) and select that drive. The process is the same as for internal drives.

Q: What’s the difference between “Size” and “Size on disk”?
A: “Size” is the actual file size. “Size on disk” includes allocation units – it can be larger because of cluster sizes. Use “Size” for comparison.

General steps for current mainstream versions; menus can differ by device and version. See the disclaimer or report an error.

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