The Test
We use xz -9 as our baseline — it's widely regarded as the strongest general-purpose compressor available and the standard benchmark for maximum compression.
We took a 26.1GB Windows CBS (Component-Based Servicing) log file — the kind generated by Windows Update and servicing stack operations — and ran it through xz at maximum compression, then through Smallest.zip.
CBS logs contain detailed records of Windows component installation, update, and repair operations. A typical line looks like:
2016-09-28 04:30:30, Info CBS Loaded Servicing Stack v6.1.7601.23505 with Core: C:\Windows\winsxs\amd64_microsoft-windows-servicingstack_31bf3856ad364e35_6.1.7601.23505_none_681aa442f6fed7f0\cbscore.dll
Results
| Compressor | Size | vs xz -9 |
|---|---|---|
| xz -9 | 156.0 MB | baseline |
| Smallest.zip | 26.0 MB | -93.2% |
Smallest.zip compresses the CBS log to 26MB — that's 99.9% smaller than the original 26.1GB file, and 93.2% smaller than xz at maximum compression.
Key Takeaways
This is our largest benchmark file yet at 26.1GB. CBS logs are highly structured — repeated component names, WinSxS paths, GUIDs, and version strings — but traditional compressors struggle to fully exploit that structure at this scale.
xz brings the file down to 156MB, which is already impressive. Smallest.zip goes 6x further, producing output that fits in just 26MB. That's a 1,000:1 compression ratio from the original file.
For Windows administrators managing fleets of machines, CBS logs are a major storage sink. Compressing with Smallest.zip means storing 26MB instead of 156MB per server — a dramatic reduction in log storage costs.
Try It Yourself
Upload your own files at smallest.zip and see the difference. Every account starts with free credits.