7Z File (What It Is and How to Open One) - Lifewire ezyZip, B1 Online Archive, and Unzip-Online are a few free online 7Z file openers.The home site for development versions (i.e., may be buggy or subject to change or include experimental features) is, and the place to go for questions about the library is the png-mng-implement mailing list. It supports almost all PNG features, is extensible, and has been extensively tested for over 23 years. libpng is the official PNG reference library.