I’m building a “compress to exact KB/MB” tool — what would make it feel trustworthy/useful? (maker feedback)

Hey Digg — I’m the maker of a small browser-based tool that compresses images to a target size (e.g., 20KB / 200KB / 1MB). It runs locally in the browser (no uploads). I’m not here to drop links — I’m here to learn from designers who deal with real submission/upload constraints.