The XDA post that made the rounds this month put a number on a trick most PC gamers underuse: transparent NTFS compression shrank a full Steam library by around 400 gigabytes for the cost of a few CPU cycles per read. On modern hardware the frame-time cost is close to noise, and the savings buy back an evening of “which game do I have to uninstall”. The best apps for Steam library compression on Windows are the ones that make that trick safe, reversible and visible. This round-up covers the compressor itself, the disk-usage tools that show you what to compress first, and the cleaners that catch the leftovers Steam’s own uninstall misses.
What to look for in a Steam library compression app
Algorithm choice sits at the top. Windows’ built-in compact command supports four LZX/XPRESS modes with different speed and ratio trade-offs. A tool that surfaces them rather than forcing a default is worth using.
Preview and reversibility matter as much as ratio. NTFS compression is transparent to the game and undoable, but a good tool logs what it touched so you can undo one game rather than the whole drive.
Read-only usage patterns are the important detail. Games spend most of their time reading assets, not writing them, which is exactly where transparent compression is cheap. A tool that identifies write-heavy directories (save files, cache) and skips them saves headaches.
Disk-usage visualisation is the other half. A treemap that shows which title ate 220 gigabytes tells you where compression pays off. Whole-library scans miss the point.
Update handling is the recurring cost. Steam updates decompress touched files. A tool that supports scheduled re-compression is worth more than one that runs once.
Quick comparison
| App | Best for | Free plan | Compression modes | Standout |
|---|---|---|---|---|
| CompactGUI | Guided per-folder compression | Fully free (open source) | XPRESS4/8/16K, LZX | Preview ratio before committing |
| Windows compact.exe | Scriptable batch compression | Included with Windows | All four NTFS modes | No install, works over SSH |
| WizTree | Fastest treemap of the disk | Free for personal use | Read-only | Reads MFT directly, no scan needed |
| Everything | Finding one huge asset fast | Fully free | Read-only | Instant name-based search |
| SpaceSniffer | Visual disk map for beginners | Fully free | Read-only | Live-updating treemap |
| TreeSize Free | Reporting to CSV for later diffs | Free with paid tier | Read-only | Column-based sortable views |
| IObit Uninstaller | Removing leftovers Steam misses | Free with paid tier | N/A | Deep-scan for registry and folders |
The apps
1. CompactGUI, best for guided per-folder compression
CompactGUI is the open-source front end to Windows’ built-in compressor. Point it at a Steam game folder, it estimates the saving with each of the four LZX/XPRESS algorithms, and you pick one. Once compressed, the game appears identical to Steam and to Windows Explorer, just smaller. The community fork at IridiumIO/CompactGUI is the version we run because it handles multi-drive setups and re-compression after Steam updates.
Where it falls short: the current fork is Windows 10 and 11 only. Very old titles that stream assets differently see smaller wins.
Pricing: Free and open source.
Platforms: Windows 10, Windows 11.
Download: CompactGUI on GitHub · Releases
Bottom line: The default pick. Sensible defaults, visible previews, and it undoes cleanly.
2. Windows compact.exe, best for scripting and unattended batches
compact.exe is the same engine CompactGUI drives, exposed as a command-line binary that ships with every recent Windows install. compact /c /s /a /i /exe:LZX "D:\SteamLibrary\steamapps\common\<game>" compresses one game folder using LZX (the highest ratio). A batch file that iterates over steamapps\common handles a whole drive in one run and slots into Task Scheduler for post-update passes.
Where it falls short: no preview and no undo history; you have to trust the command and log to a file. Wrong flag on the wrong path is a real risk on a shared machine.
Pricing: Free with Windows.
Platforms: Windows 10, Windows 11.
Download: Built in. compact /? from an admin PowerShell shows every flag.
Bottom line: Use it when a script beats a click, or when you want to re-compress a folder after Steam updates it.
3. WizTree, best for finding the largest games in seconds
WizTree reads the NTFS Master File Table directly instead of walking directories, so it finishes a two-terabyte drive scan in a few seconds. The treemap and the file-list view both sort by size, which is the fastest way to spot the four or five games eating half the drive.
Where it falls short: the free personal build hides some sorting features that the paid one exposes. Non-NTFS drives fall back to a slower scan.
Pricing: Free for personal use. WizTree Pro is around $20 per year.
Platforms: Windows 10, Windows 11.
Download: WizTree site · Portable download
Bottom line: Run it first, decide what to compress second.
4. Everything, best for finding one huge asset fast
Everything by voidtools is not a disk-usage tool, it’s the fastest name-based file search on Windows. Once its index is built (seconds on NVMe), typing size:>2gb ext:pak shows every large asset pack across every drive in real time. Combined with a treemap tool, it isolates the one game update or DLC pack that suddenly ate 40 gigabytes.
Where it falls short: search-only, no treemap, no compression. It sits alongside CompactGUI rather than replacing anything.
Pricing: Fully free.
Platforms: Windows 10, Windows 11.
Download: voidtools site
Bottom line: Keep it in Startup. The moment your drive fills, it saves the next twenty minutes.
5. SpaceSniffer, best for a live-updating disk map
SpaceSniffer paints the whole drive as a nested treemap and refreshes it as Steam and Windows write new files. It’s easier to explain to a non-technical household member than TreeSize is, and its filter box handles queries like >500mb :older 30days for games that haven’t been touched in a month, which are the strongest candidates for compression.
Where it falls short: development has slowed; the interface is dated. Very large drives can take a couple of minutes to scan.
Pricing: Fully free (donationware).
Platforms: Windows 10, Windows 11.
Download: SpaceSniffer site
Bottom line: Pick it when someone else on the PC will use the tool too.
6. TreeSize Free, best for reporting to CSV
TreeSize Free by JAM Software gives you a directory-tree view with columns for size, files, folders, oldest and newest write. Export to CSV lets you diff the same drive before and after a compression run, or track which games are growing between Steam updates. It sits alongside CompactGUI as the audit tool.
Where it falls short: the free tier caps some features (network shares, size on disk vs. size); the paid Professional edition unlocks them.
Pricing: Free tier. TreeSize Professional starts around $60 one-time.
Platforms: Windows 10, Windows 11.
Download: JAM Software site
Bottom line: The right pick when a screenshot is not enough and you want a report.
7. IObit Uninstaller, best for cleaning up leftover files
IObit Uninstaller is the last-mile tool: after removing a game through Steam, its Deep Scan finds the leftover shader caches, mod folders, launcher configs and registry entries that Steam leaves behind. Reclaimed space per title is usually small, but across a big library it adds up, and it prevents “why is my drive still full” after mass uninstalls.
Where it falls short: the free tier suggests upgrades; the pro tier is the one to pick if you care about scheduled scans. Not open source.
Pricing: Free tier. Pro starts around $20 per year.
Platforms: Windows 10, Windows 11.
Download: IObit site
Bottom line: Pair with CompactGUI: compress what you keep, purge the rest.
How to pick the right one
For the compression itself: CompactGUI on desktop, compact.exe in a script. Both drive the same engine; pick whichever fits how you work.
For the “what should I compress first” question: WizTree if you want it in seconds, SpaceSniffer if you want a live picture.
For repeat auditing on a shared machine: TreeSize Free with CSV exports, then diff runs monthly.
For the last-mile cleanup after uninstalling: IObit Uninstaller with Deep Scan enabled.
For finding the one 40-gigabyte asset pack that showed up overnight: Everything.
FAQ
Does NTFS compression hurt game performance?
On any recent CPU the read-time decompression cost is small and predictable. XPRESS modes are cheaper than LZX; XPRESS8K is a common default for game folders. Modern SSDs are the bottleneck, not the CPU, so the net effect on load times is usually a small improvement, not a regression.
Will Steam updates undo the compression?
Files Steam rewrites during an update come back uncompressed. Re-run CompactGUI (or your compact.exe script) after major patches. On a heavy update schedule, a weekly scheduled task keeps the compression fresh.
Which algorithm gives the highest ratio?
LZX in most cases, at the cost of the longest initial compression pass. XPRESS16K is a fair compromise. Preview both in CompactGUI on a small game before committing to a full library.
Can I compress the whole D:\SteamLibrary folder at once?
Yes, and it’s the fastest way. Point CompactGUI or compact at the top-level library folder and let it recurse. Skip Steam’s downloading and temp directories; write-heavy folders don’t benefit from transparent compression.
Is any of this risky?
NTFS compression is a standard Windows feature and fully reversible; compact /u decompresses. The real risks are running admin commands on the wrong drive letter and running out of disk mid-pass (compressing files needs a small temporary buffer). Keep enough free space to survive a mid-run stop.
