Donorbox donation pages have two image slots with two very different budgets, and both cap at 1MB. The donation-form header image is limited to 692x550 pixels and 1MB, while the campaign background artwork is designed at 1920x1080 with a 1720x580 safe zone and also needs to come in under 1MB — with the logo at 140px tall under the same cap. A 1920x1080 photograph at full quality is routinely 2-4MB, so the background is the one that fails. Compressing a full-bleed background is also where quality matters least and file size matters most: nobody studies the blurred edges of a hero image, but everybody notices a form that takes four seconds to paint. Skwish compresses in the browser with a per-file readout, so you can find the quality point where a 1920x1080 background lands at 700-900KB, then batch the rest of the campaign imagery and export a ZIP. Files never leave your device.