Measured - byte-exact - 2026

Pedulli vs zlib-ng

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

TL;DR - honest
zlib-ng is the modern drop-in zlib replacement - same DEFLATE output as gzip, but several times faster on AVX2 CPUs. Pedulli is a best-of-N racer: it runs several internal coders and keeps the smallest output, always byte-exact (SHA-256 roundtrip) with a +1 byte never-worse floor. Pedulli wins ratio across every structured class measured here; zlib-ng wins throughput when you need DEFLATE-compatible output on the wire.

The measured table

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

Input	zlib-ng -9	Pedulli (best-of-N)	Δ
1 MiB of zeros	1,041 B	13 B	much smaller (redundant input)
JSON 31 KB	4,820 B	1,265 B	-73.7%
HTML 161 KB	52,103 B	38,757 B	-25.6%
MP4 master 10 MB	9,742,892 B	9,430,108 B	-312 KB
Random bytes 1 MB	1,048,768 B (+192 B)	1,048,577 B (+1 B)	191 B less overhead

What zlib-ng does better (honest)

DEFLATE-compatible output. Drop-in for zlib/gzip: HTTP Content-Encoding: gzip, PNG, ZIP archives all decode it unchanged.
SIMD throughput. Several times faster than stock zlib on modern AVX2 CPUs - far faster than a service round-trip.
In-process library. No API call to make.

What Pedulli does that zlib-ng does not

+1 byte never-worse floor. Pedulli's own output is never more than 1 byte over the input; zlib-ng (DEFLATE) adds tens to hundreds of bytes on incompressible data.
Best-of-N racing. Several internal coders race rather than one DEFLATE pass, so JSON, HTML and MP4 classes come out tighter.
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 zlib-ng for high-throughput DEFLATE-compatible streaming (HTTP Content-Encoding: gzip, PNG, ZIP archives). Use Pedulli for cold storage, archives, anything where ratio matters more than wire compatibility, plus the per-file +1 byte never-worse floor.

Run the free trial Pricing / API All benchmarks

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