How JPEG compression works
JPEG throws away detail your eye is unlikely to notice, and the quality setting decides how much. Most cameras and phones save at a very high quality, so their files carry far more data than you can see. Re-encoding at around 80% removes much of that excess with no visible change at normal viewing sizes.
Squeezels uses mozjpeg, Mozilla's improved JPEG encoder. It produces standard JPEGs that open everywhere, but tunes them more carefully, with smarter quantisation and progressive encoding, so you get a smaller file at the same quality.
The biggest win: size
A modern camera photo is often 6,000 pixels wide or more. Shown on a website, in an email or in a slide deck, it rarely needs more than 2,560. Resizing removes most of the bytes before compression even starts. The example above was resized to 2,560 pixels at quality 80%. Keep your full-size originals for printing and editing.
Re-compressing an already compressed JPEG
Every JPEG re-encode is lossy, so Squeezels never makes a file bigger to “compress” it. If a photo was already saved efficiently, re-encoding at the same size and quality may not save anything. In that case Squeezels keeps your original exactly as it was.
