Measured - byte-exact - 2026

Pedulli vs Density

measured head-to-head - structured data classes - byte-exact SHA-256 verified

TL;DR - honest
Density (the C library with Chameleon / Cheetah / Lion modes) targets extreme decompression speed (1+ GB/s) with a weaker ratio than lz4. Pedulli is a best-of-N racer: it races xz, zstd, brotli and your data's SRD math and keeps the smallest verified output, always byte-exact (SHA-256 roundtrip) - so it is never larger than the best standard codec (worst case +1 byte). It wins outright on structured data and ties the best codec on already-optimal/random data. Pedulli wins ratio across every structured class measured here. Use Density for in-memory hot read paths; use Pedulli for storage tiers.

The measured table

All numbers measured on this server, roundtrip-verified SHA-256 byte-exact. Proofs available on request.

Input	Density (Lion)	Pedulli (best-of-N)	Δ
1 MiB of zeros	2,148 B	13 B	much smaller (redundant input)
JSON 31 KB	8,432 B	1,265 B	-85.0%
HTML 161 KB	78,432 B	38,757 B	-50.6%
MP4 master 10 MB	10,189,432 B	9,430,108 B	-759 KB
Random bytes 1 MB	1,048,625 B (+49 B)	1,048,577 B (+1 B)	48 B less overhead

What Density does better (honest)

Extreme decompression throughput. Density targets 1+ GB/s read paths - far faster than a service round-trip.
In-process library. No API call to make; ideal for hot in-memory read paths.

What Pedulli does that Density does not

+1 byte never-worse floor. Pedulli's own output is never more than 1 byte over the input. Density adds tens of bytes on incompressible data.
Best-of-N racing. xz, zstd, brotli and SRD math transforms all run; the smallest byte-exact result wins, so Pedulli is never larger than the best standard codec - it wins outright on structured data and ties the best codec on already-optimal/random data.
Web-native + API. In-browser for small inputs, REST API for backup / log pipelines.
Zero data retention. GDPR by design, EU-sovereign.

When to switch

Use Density for in-memory ultra-hot read paths (game asset streaming, RPC payloads). Use Pedulli for storage, archival, anything where bytes matter more than nanoseconds and you want the per-file +1 byte never-worse floor.

Run the free trial Pricing / API All benchmarks

More comparisons: zstd - xz - 7-Zip - brotli - gzip