APNG

APNG is an unofficial extension of the PNG image format. It supports animation very similar to animated GIF.

APNG files are valid PNG files. When an APNG file is viewed in a program that does not support the APNG extensions, it will appear as a still image chosen by the creator of the APNG file.

Specifications

 * APNG Specification

Sample files

 * http://littlesvr.ca/apng/samples.html
 * http://people.mozilla.com/~dolske/apng/demo.html