The ANI file format is a graphics file format used for animated mouse cursors on the Microsoft Windows operating system.[1]
The format is based on the Microsoft Resource Interchange File Format, which is used as a container for storing the individual frames (which are standard Windows icons) of the animation.
Animated cursors contain the following information: (in order of position in the file)
Frame rates are measured in jiffies, with one jiffy equal to 1/60 of a second, or 16.666 ms.
Sequence information present in the file determines the sequence of frames, and allows frames to be played more than once, or in a different order than that in which they appear in the file. For example, if the animation contains three different images numbered 1, 2 and 3, and the sequence is 1-2-3-2-1, (five frames) then only three icons need to be stored in the file, thereby saving storage space.