Files with the .TN3 extension contain animated graphics – multiple frames consisting of bitmap images, as well as information regarding the tempo and length of the animation. It was used in Atari ST systems between the end of the 1980s and beginning of the 1990s for animating high-resolution bitmaps.

Atari ST also supported so-called Tiny formats for low and medium resolution animations, named TN1 and TN2 respectively.