A Kindle eBook fails on image quality for a specific, documented reason: KDP calls anything under 200 DPI low resolution and asks for a minimum of 300 DPI, sized at 100% and flattened to one layer. That definition is about pixels per inch at the size the image is displayed, not about file weight. It follows that the wrong fix for a bloated manuscript is to downscale every image, because downscaling lowers the DPI at the same display size, which is the exact thing KDP flags. The right fix is to compress the encoding while leaving the pixel dimensions alone: same width and height, fewer bytes per pixel. Where you do resize, resize down from an oversized original only, and never enlarge a small image to reach a number — KDP says enlarging decreases resolution, and that manually altering the DPI reading does not add real detail. Skwish gives you a size target and an exact-dimension resize as separate controls, so you can cut bytes without touching pixels. It runs in your browser, which matters for manuscripts with a lot of figures: nothing leaves the machine.