Out of the vast universe of available photo gallery software packages, Piwigo distinguishes itself with a snappy user interface and a set of customizable features. Foremost among these features is a category "tree" which lets users create photo categories that expand and flatten the tree structure to view all the photos. Visitors can also set up user permissions and also create rating tabs for each photo, or groups of photos. This version is compatible with computers running Mac OS 10.3 or newer or Windows 95 and newer.