Compress an image

The quality slider starts at 70%, which is where most photographs stop looking any better and keep getting bigger. The original and the result are laid on top of each other with a line you drag between them, and you can zoom to 8× — so the trade-off is one you can actually look at rather than a number you are asked to trust.

The encoders are the ones Squoosh uses — MozJPEG, libwebp, libavif and oxipng — rather than the browser's own, which matters: at the same setting MozJPEG reaches about a quarter fewer bytes than the canvas encoder, and PNG gets smaller at all, which through the browser it never did.

Converting to WebP usually saves more than lowering JPEG quality does, and often at higher visual quality. Resizing saves more than either: an image displayed 800 pixels wide gains nothing from being 4000.

Nothing is written until you press download and the original is never modified, so you can push the slider until it visibly breaks and then come back. A batch compresses together once the images are selected, and each keeps its own setting if one of them needs treating differently from the rest.