Speed is everything on the internet, and as a general rule of thumb: the smaller the file, the faster it’ll load. To help with that, Google created a new open-source JPEG encoder that will purportedly reduce the file sizes of images while maintaining picture quality, allowing websites to load faster.
The new encoder is called Guetzli — Swiss German for “cookie,” apparently — and according to Google, it can create “high quality JPEG images with file sizes 35 percent smaller than currently available methods.” The advantage to using Guetzli instead of a new format is that the images are still regular JPEG files, and so they’re still compatible with almost every browser and application that exists.
Google has several other projects to reduce image sizes on the web, including its Zopfli encoder (which similarly creates smaller PNG files without breaking format compatibility) and WebP (a new image format that supports both lossless and lossy compression for improved file sizes).
According to Google, Guetzli does take “significantly longer” to compress images than other methods of JPEG encoding, but it feels that the slower speed in creating the image is worth the speed gains when loading it. Additionally, the company cites a Google Research paper that claims that users found the Guetzli images to be of higher quality than similar and even larger JPEG files created with other methods.
For more details on the nitty-gritty of how Guetzli actually accomplishes the improved encoding (it apparently involves “psychovisual models”) check out the Google Research Blog and the published paper on Guetzli.