Why a size target beats a quality slider
A single quality setting produces wildly different file sizes depending on the image. A flat product shot on a white background compresses to a fraction of what a detailed, textured photo does at the identical setting. So a batch exported at “quality 80” comes out anywhere from 200 KB to 3 MB, and if you had a limit to hit, some of them missed it.
Setting a byte target instead makes the tool search for the best quality each individual image can afford. Every file lands under the limit, and none of them are compressed harder than they needed to be.
Resize first, compress second
If a file is far too large, compression is the wrong lever to pull first. Pixel count dominates: halving the dimensions removes three quarters of the pixels before a compressor does anything, and the result looks better than the same file size reached by crushing quality alone.
A practical rule for listing photos: set the dimensions to what the destination actually displays, then compress to the limit. That order gets you the best-looking image that fits.
Where the limits come from
Etsy warns that images above about 1 MB often fail to finish uploading on slower connections. Daraz caps files at 5 MB. Amazon prefers JPEGs under 10 MB. Most email systems balk somewhere around 20 MB for a whole message. These are the numbers people are usually trying to get under, and each marketplace page linked below states its own.
Nothing is uploaded
Compression runs in your browser using your own device. This matters more than usual for a compressor, because compressing a file means handing over the full-quality original — and here there is nobody to hand it to.
Common questions
How do I compress an image to under 1 MB?
Turn on "Target a file size instead" and enter 1000 KB. The tool then searches for the highest quality setting that still fits under that limit, per image, rather than applying one quality percentage to everything.
What is the difference between compressing and resizing?
Resizing changes the pixel dimensions. Compressing keeps the dimensions and reduces how many bytes are used to store them. For a file that is too large, resizing usually saves far more than compression does — a 4000 px photo scaled to 2000 px is a quarter of the pixels before any compression is applied.
Will compression make my product photos look bad?
Not at sensible settings. On photographic content, quality in the low 80s is effectively indistinguishable from maximum while being a fraction of the size. Visible artefacts start appearing well below that, which is why the file-size search here will not go below 40.
Which format compresses best?
WebP is typically 25 to 35 percent smaller than JPEG at equivalent visual quality and supports transparency. JPEG is more universally accepted by older systems and every marketplace. If the destination accepts WebP, use it; if you are unsure, use JPEG.