WinDirStat ^[1] is a port of KDirStat for Linux ^[2]. It's free, lightweight, small (650kb installer), fast, portable (as a standalone .exe file), and works on multiple versions of Windows. Besides showing folders and percentages (for the entire disk or any subset of folders), it also displays an (optional) graphical usage map. Works well with NTFS Junction folders, avoiding counting folders multiple times.

SpaceSniffer ^[1] is another possibility. It can scan Alternate Data Streams (ADS) and correctly ignores junctions. However, it is not hard-link aware. If a file has multiple links, they will show up in the scan more than once. I've personally tested all this information to be accurate on Windows XP as of version 1.1.2.0.

TreeSize ^[1] is pretty sweet.

Its advantage over the others is that on NTFS drives, it works on the MFT (Master File Table) and reaches extremely high scan speeds.

They have three versions of the product: Free ^[2], Personal ^[3] and Professional ^[4].

The free version doesn't have fancy visualizations and reports but should be sufficient in most cases.

JDiskReport ^[1] (also available for Mac OS X and Linux).

I tend to stick with Scanner ^[1]. I occasionally try programs with more features, but I find Scanner does everything I actually need.

I've always used, and liked, SpaceMonger ^[1]. There is a paid-for newer version, but the old version ^[2] works fine for my needs.

I like FolderSize ^[1], since it's integrated into Explorer and caches the results. You always know how much space a folder is taking, and can easily identify space hogs. It's always there, so you don't have to start a separate program.

It's old, but I really like the tree map view in SequoiaView ^[1].

SequoiaView is free and happily works all the way up to Windows 7 and Server 2008.

I'd recommend Disk Space Fan ^[1]. It has a similar UI to Scanner or Overdisk, but looks more fashionable. Current price for a single license in 15$.

With Sysinternal suite ^[1], you have du.
I like it, because it is command-line, very lean and fast. And it is free :-)

C:\>du somedir

Du v1.33 - report directory disk usage
Copyright (C) 2005-2007 Mark Russinovich
Sysinternals - www.sysinternals.com

Files:        28618
Directories:  2625
Size:         671,672,063 bytes
Size on disk: 671,672,063 bytes


C:\>

WizTree ^[1] is free and can read directly MFT, so in contrast to most other programs it scan in seconds.

There are many possibilities, but in my opinion the best programs to show file system usage are: WinDirstat, Scanner, Xinorbis and SpaceSniffer.

• Scanner ^[1]
• WinDirStat ^[2]
• FolderSize ^[3]
• SpaceSniffer ^[4]
• overdisk ^[5]
• JDiskReport ^[6] (requires java)
• SequoiaView ^[7]

limited

• Disk Space Fan ^[8]

not free

• SpaceMonge ^[9]r
• TreeSize ^[10]
• DiskView ^[11]

not found

• Drivespacio ^[12]

References:

Overdisk alternatives ^[13]

How can I visualize the file system usage on Windows? ^[14]

Herramientas para analizar el espacio en disco ^[15]

DiskView ^[1] is very handy. It has both the pie chart visualization as well as usage bars on the folder tree. It's integrated directly into Windows Explorer.

The older edition of SpaceMonger ^[1] is minimalist and functional.

While WinDirStat shows a similar view, I prefer the higher contrast, visiblity of SpaceMonger when I want to quickly view the state of my drive.

I've always used OverDisk ( web search ^[1]). Simple and effective.

Notes:

• OverDisk's old URL ^[2] (http://users.forthnet.gr/pat/efotinis/programs/overdisk.html) appears to be dead
• other questions ^[3] indicate OverDisk is incompatible with Windows 10

SizeReporter is a tool I wrote that comes with no GUI. The main trigger for creating this tool was to have a way to run a disk space reporting application under a service and get raw data only. Further processing and own reporting/diagramming can then be done in a custom way by using other Software. I was amazed that for Windows I could not find anything free that actually fit my needs.

The tool is not actually really spectacular but can deal with many quirks and issues on filesystems (bad timestamps, very long paths, junctions, ...). "du" (sysinternals) was the tool I used in the past but delivers only a summary.

I hope this can also be useful to others.

SizeReporter download page ^[1]

Folder Size ^[1]'s documentation ^[2] says that cannot be done because API has been removed ^[3] since Windows Vista.

There are few standalone apps exists for folder size checking, like TreeSize Free ^[4].

I've recently found another (rather unimaginative title) FolderSize ^[1] software from MindGems:

There are freeware and portable versions here ^[2].

As of Windows 10, there is a built-in utility for this. Navigate to Settings and then Storage.

Click on "Show more categories" at the bottom to get the full picture:

Clicking the "Other" section will display the folders taking up the most space. For example:

FolderSize.Win32 ^[1] is ultimate one. You can use the scroll button to peek in and out of folders and easily find out any deep nested folder which is consuming lot of space.

Shows everything visually. Very very nice.

I see WinDirStat has been given a few mentions already - so I'll just throw ShowMan ^[1] into the mix.

I like the display of ShowMan better than WinDirStat, as it's cleaner to look at. However - ShowMan is not free for commercial use (and for that reason, I have been using WinDirStat more recently).

It seems every disk space analyser under the sun has been listed and the one with the most votes hasn't had a new release since the question was asked seven years ago!

I recommend Folder Size Explorer ^[1], one of the newest and simplest disk space analyzers that can quickly display which folders are using the most disk space and also export the list for printing. It has the same familiar functionality as the built-in Windows Explorer so it's very intuitive.

I use Glary Utilities ^[1] which is free with lots of useful tools in different categories.

There is a Disk Space Analyzer which is can help.