How the two modes differ
By Percentage keeps the image at full resolution and only lowers quality — good when you want a predictable size reduction and don't mind a bit of extra softness. Target KB works the other way: it holds quality as clean as it can and only shrinks the pixel dimensions if quality alone can't hit your target — better when you have a hard limit (an upload cap, an email attachment size) and care more about hitting it exactly than about resolution. Both run entirely by re-encoding the image in your browser's canvas; nothing is uploaded anywhere.
Common questions
Does compressing shrink the image's width and height?
Only in Target KB mode, and only if quality reduction alone can't reach your target size — it'll then reduce resolution as a last resort. By Percentage mode never touches the dimensions, only the encoding quality.
Will a transparent PNG stay transparent?
Yes, as long as you export as PNG or WebP — both support transparency. Choosing JPEG output will flatten transparent areas to white, since JPEG has no alpha channel.
Is there a limit on file size or how many images at once?
Each file is capped at 50 MB — anything larger is rejected before it's added. There's no cap on how many images you add at once, though very large batches will use more of your browser's memory and can get slow depending on your device.
Does compressing twice keep shrinking the file?
A little, but with fast diminishing returns and visibly worse quality — JPEG/WebP are lossy, so each re-encode compounds the artifacts. Compress from the original file each time rather than re-compressing an already-compressed copy.