Which organization developed APNG in 2004?

The Mozilla Foundation developed APNG in 2004.

APNG, or Animated Portable Network Graphics, was proposed by Mozilla developers Stuart Parmenter and Vladimir Vukićević. They designed it to provide animation for interface elements such as browser throbbers while retaining PNG’s strengths, including lossless compression, high color depth, and alpha transparency.

An APNG file is structured so that its first frame can be read as an ordinary PNG image. Additional animation data is stored in PNG chunks that describe frame timing and subsequent frames. This backward-compatible design means software without APNG support can often still display the first frame instead of showing nothing.

APNG emerged partly as a simpler alternative to MNG, a more elaborate animated-image format associated with the PNG project. The PNG Development Group initially rejected APNG as an official PNG extension in 2007, but browser and software support continued to grow. It is now supported by major modern browsers and is widely used for animated stickers and interface graphics.