Overview
NTFS compression is a built-in Windows feature that shrinks files and folders to save disk space, transparently decompressing them when accessed. It can be useful, but it is not right for every situation. This guide covers the trade-offs and how to enable it.
Key Takeaways
- NTFS compression saves space and is transparent to apps.
- It trades a little CPU for smaller file sizes.
- Best for rarely used, compressible files (text, documents, logs).
- Avoid it for already-compressed media, system files, and games on fast storage.
How It Affects Performance
Compressed files use more CPU to read/write because Windows decompresses them on the fly. On modern CPUs with slower (HDD) storage, this can even speed up reads slightly; on fast SSDs with large active files, it can add overhead.
When Compression Is Useful
- Large amounts of text, documents, logs, or other highly compressible data.
- Archive folders you rarely open.
- Drives that are short on space where the files are compressible.
When to Avoid It
- Already-compressed files (JPEG, MP4, ZIP) — little space is saved and CPU is wasted.
- System and program files, and games, where performance matters.
- Very large active databases or frequently written files.
Enable Compression on a Folder
1. Right-click the folder and choose Properties.
2. On the General tab, click Advanced.
3. Tick "Compress contents to save disk space" and click OK.
4. Choose to apply to the folder and all subfolders/files, then OK. Compressed items show in a different colour.
Enable Compression on a Whole Drive
1. Open This PC, right-click the drive, and choose Properties.
2. On the General tab, tick "Compress this drive to save disk space".
3. Click OK and apply to the drive and subfolders.
4. Allow time for Windows to compress existing files.
Warning: Do not compress the drive that holds Windows for performance-sensitive systems; compress specific folders of compressible data instead.
Troubleshooting
Problem: Compression saved almost no space.
Solution: The files were already compressed (media/archives). NTFS compression mainly helps text and uncompressed data.
Problem: The PC feels slower after compressing.
Solution: Decompress performance-sensitive folders (untick the Advanced compression option); reserve compression for rarely used data.
Problem: I cannot compress some files.
Solution: System files and files in use may be skipped; compress when they are not active, and avoid the active Windows folder.
Problem: How do I undo it?
Solution: Open the folder/drive Advanced properties (or Properties) and untick the compression option; Windows decompresses the files.
Conclusion
NTFS compression is a handy, transparent way to reclaim space — best applied to compressible, infrequently used data. Avoid compressing media, system files, and performance-critical drives, and you will get the benefit without the downside.
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