Mozjpeg Gives Smaller White-Background JPEGs With Fewer Off-White Pixels Than Pillow or Sharp

A developer compared Pillow, sharp, and sharp with its mozjpeg option for saving white-background product photos as JPEG. Pillow and default sharp produced identical pixels, while the mozjpeg flag yielded smaller files with fewer stray non-white background pixels at the same quality. None of the encoders kept the background at a pure 255 value across every pixel. The tests were run on three Wikimedia Commons photos using an Apple M4 Mac with Pillow 11.3.0 and sharp 0.34.5. The author found mozjpeg at quality 85 with 4:4:4 sampling roughly matched Pillow at quality 95 in stray-pixel share while using less than half the bytes.