What I like the most about it, is the fact that it gives you flexibility in decreasing the number of colors so you can determine how much is enough in terms of compression.
Begin with selecting as much as 20 PNG files from you computer, then upload queue. Use thumbnails in order to pick images. Decrease the number of colors with the color slider for optimum compression.
BMP, ICO, GIF and JPG files are also supported through auto conversion to PNG.
- Source: http://compresspng.com/