Pngquant is a free, open source and cross-platform command-line lossy PNG compressor. It is based on a portable libimagequant library and is written in C99. It reduces the file size significantly by converting the PNG image to more efficient 8-bit PNG format and preserves full alpha transparency. As you may already know, 8-bit PNG files are often 60-80% smaller than 24/32-bit PNG files. The images compressed using Pngquant are fully-compatible with all web browsers and operating systems. Pngquant can compress one or multiple images at once.