image/x-png

This mimetype is deprecated. You should still support it, but avoid using it to assign new mimetypes.
Instead, please use image/png

Portable Network Graphics (PNG) was devised starting in a discussion on newsgroup comp.graphics in 1995, with the first version of its specification released in 1996. The motivation for its creation was to create a free and unencumbered image format in the wake of the patent issue with GIF.

File types

.png

Also appears as

Further reading

  1. Internet Assigned Numbers Authority (IANA)
  2. Let's Solve the File Format Problem!