Image Compression Benchmark
Same image, four codecs, real numbers. We compressed one sample through zipo.pics and measured the actual output — no marketing, just bytes. Use it to decide which format to pick before you compress.
| Format | Output size | vs original | When to use |
|---|---|---|---|
| PNG (lossless) | 12.8 KB | −75% | Best when every pixel must survive — logos, screenshots. |
| JPG | 2.1 KB | −96% | Universally compatible; great for photos. |
| WebP | 0.9 KB | −98% | Smallest here — simple codec wins on tiny smooth images. |
| AVIF | 1.3 KB | −97% | Usually beats WebP on photos; overhead shows on micro images. |
How we measured
The test used one source image and ran it through the same compression engine zipo.pics ships in the browser — Rust compiled to WebAssembly, with no server in the loop. Each format was encoded with default settings and the final byte size was read directly from the output file. Nothing was averaged, estimated, or hand-picked; the table shows the exact bytes the engine produced. Because the engine runs locally, the numbers reflect the codec, not a network or a CDN.
The counterintuitive part: AVIF was not the smallest
On this tiny, smooth gradient image AVIF (1.3 KB) came in larger than WebP (0.9 KB). AVIF’s more advanced encoder carries fixed overhead that only pays off on detailed, larger images — so on micro, low-detail graphics WebP can win. On real photos, AVIF usually pulls ahead of WebP. There is no single "best" codec; it depends on your image.
How to read this table
The "vs original" column is the honest headline: even the lossless PNG dropped 75% because the source itself was an uncompressed 50.9 KB export. The takeaway is not "AVIF is always smallest" — it is "pick the format to match the image". Photos lean WebP/AVIF, universal compatibility leans JPG, and anything that must stay pixel-perfect stays PNG. The only way to know the real number for your file is to compress it.
Questions people ask
Why is the lossless PNG smaller than the original?
The 50.9 KB original was an uncompressed export. PNG re-encodes it losslessly and strips that waste, landing at 12.8 KB while keeping every pixel identical. "Lossless" means no quality loss, not "no size change".
Should I always use WebP then?
For photos on the modern web, WebP (or AVIF) is usually the smallest at good quality. But older editors, some print pipelines and a few CMSes still expect JPG or PNG. Match the format to where the image will be used, not to a ranking.