The MIME type image/png is used to denote the presence of Portable Network Graphics format images. The category for this MIME type is "image".

The images stored in the Portable Network Graphics usually carry the extension PNG. Portable Network Graphics or PNG is a bitmapped image format that compresses image data in a lossless manner. PNG was created to improve upon and replace GIF (Graphics Interchange Format), where both are image-file formats that do not require patent license.

PNG supports images that are palette-based (24-bit RGB color palettes), greyscale, RGB or RGBA images. PNG does not support color spaces such as CMYK because it was always meant to be a format for sending images over the Internet and not a professional format.

PNG was created when it was discovered that a company called Unisys had patented the Lempel-Ziv-Welch (LZW) algorithm used for the data compression of GIF images. There were also other factors involved, such as the limitation of GIF to 256 colors. This was happening in the year 1995 and by then the displays had evolved to produce much more than just 256 colors. Even though GIF also allowed animation, its replacement, the PNG format was made to be a single image format.