Compress Image

Drop in an image and pull the quality slider until the size is where you want it. The compression runs on your own processor, so there is nothing to upload and nothing to wait in a queue for.

What compression actually does to a photo

JPEG compression works by throwing away detail that human vision is bad at noticing — fine colour variation first, then progressively coarser structure. The quality number controls how aggressive that discarding is. It is not a percentage of anything; it is a knob on the encoder.

The relationship between that number and file size is steeply non-linear. Dropping from 100 to 90 usually removes a large share of the file with almost no visible change, because quality 100 spends an enormous number of bits preserving detail nobody can see. Dropping from 60 to 50 removes far fewer bytes but is much more likely to show blocking in smooth areas like sky or skin.

Choosing a number instead of guessing

For photographs headed to a website or a chat app, 70 to 80 is the range that almost always holds up. The default here is 75. For images that will be printed, or that someone will edit again afterwards, stay at 90 or above — every further re-encode compounds the loss.

Screenshots, logos, line art and anything with sharp text are a different problem. JPEG handles hard edges badly and will produce visible ringing around letters no matter how high you push the quality. Those belong in PNG or WebP instead.

Why the result may surprise you

If you feed in a PNG screenshot, the JPG that comes out may be larger, not smaller. PNG is lossless and extremely efficient at flat colour, which is exactly what screenshots are made of; JPEG has to spend bits describing edges it cannot represent cleanly.

If you feed in an image that was already compressed hard once, compressing again at a high quality setting can also increase the size, because the encoder is now faithfully preserving the compression artefacts from the first pass. Compressing the same file repeatedly always degrades it — each round is a fresh loss on top of the last.

No upload, so no limits

The well known compression sites all work the same way: upload, process on their hardware, download. That model forces them to ration the free tier. One popular service caps free web uploads at 15 MB per file; another allows two tasks per hour and stamps a watermark on anything beyond that.

Breezo compresses using a WebAssembly build of the MozJPEG encoder running in your tab. No transfer, therefore no reason to ration anything. Large files, batches, and as many rounds as you like — the only ceiling is your own device.