Measured - byte-exact - 2026

Pedulli vs Zopfli

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

TL;DR - honest
Zopfli is Google's ultra-slow DEFLATE compressor (about 100x slower than gzip) that produces fully gzip-compatible output. The Pedulli Orchestrator is a best-of-N racer: it races xz, zstd, brotli and your data's SRD math, then keeps the smallest verified output, always byte-exact (SHA-256 roundtrip) with a +1 byte never-worse floor on its own output. So it is never larger than the best standard codec it races (worst case +1 byte): it wins outright on structured data and ties the best codec on already-optimal or random data. Use Zopfli only if you must emit .gz that decodes everywhere; use Pedulli otherwise.

The measured table

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

Input	Zopfli --i100	Pedulli (best-of-N)	Δ
1 MiB of zeros	1,029 B	13 B	much smaller (redundant input)
JSON 31 KB	4,389 B	1,265 B	-71.2%
HTML 161 KB	47,932 B	38,757 B	-19.1%
MP4 master 10 MB	9,732,140 B	9,430,108 B	-302 KB
Random bytes 1 MB	1,048,759 B (+183 B)	1,048,577 B (+1 B)	182 B less overhead

What Zopfli does better (honest)

Bit-compatible .gz output. Every gzip/zlib reader and browser decodes it unchanged - ideal for CDN and legacy consumers.
Tightest DEFLATE. Within the DEFLATE format Zopfli squeezes harder than gzip -9 at the cost of being very slow.
In-process tool. No API call to make.

What Pedulli does that Zopfli does not

+1 byte never-worse floor. Pedulli's own output is never more than 1 byte over the input; Zopfli (DEFLATE) adds tens to hundreds of bytes on incompressible data.
Best-of-N racing, never larger than the best codec. Pedulli races xz, zstd, brotli and your data's SRD math instead of one DEFLATE encoder, and keeps the smallest verified output - so it is never larger than the best standard codec it races (worst case +1 byte). JSON, HTML and MP4 classes come out tighter than the best DEFLATE pass; on already-optimal or random data it ties the best codec.
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 Zopfli when consumers need bit-compatible .gz output (CDN-friendly, browser-friendly). Use Pedulli when you control both ends and ratio matters, 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