Issue link: https://read.uberflip.com/i/1146286
Wikipedia | 131 None of the images has an Expires header. This is the second-most important perfor- mance improvement for Wikipedia. Some of the images haven't been modified in over a year. Adding a far future Expires header would improve the response time for millions of users, without adding much burden to the development process when images change. Also, the stylesheets should be gzipped. They currently total about 22K, and gzip- ping them would reduce the number of bytes downloaded to 16K. Most of Wikipedia's images are in PNG format. The PNG format is frequently cho- sen over GIF because of its smaller file size, as well as greater color depth and trans- parency options. It's likely that using the PNG format saved Wikipedia several kilobytes of data to download (it's not possible to convert their PNG images to GIF for comparison because of the loss of color depth). However, even after choosing the PNG format, further optimization can bring the file sizes down even more. For example, optimizing Wikipedia's 12 PNG images brought the total size from 33K down to 28K, a 15% savings. There are several PNG optimizers available—I used PngOptimizer (http://psydk.org/PngOptimizer.php). Adding a PNG optimization step to their development process would improve Wikipedia's performance.