Google's new algorithm shrinks JPEG files by 35 percent
The Guetzli encoder could literally cut down the size of the web.
...If you want to get technical, Guetzli (Swiss German for "cookie") targets the quantization stage of image compression, wherein it trades visual quality for a smaller file size. Its particular psychovisual model (yes, that's a thing) "approximates color perception and visual masking in a more thorough and detailed way than what is achievable" in current methods. The only tradeoff: Guetzli takes a little longer to run than compression options like libjpeg. Despite the increased time, Google's post assures that human raters preferred the images churned out by Guetzli. Per the example below, the uncompressed image is on the left, libjpeg-shrunk in the center and Guetzli-treated on the right.