ANI is a file extension used on Windows operating systems. The suffix is not strictly associated with any particular program or application – ANI files store system cursor animations data.

ANI file contains information about mouse cursor animations and sequence or related ICO frames. Each animation frame is displayed for a very short time in that the sequence of such frames creates a illusion of animation. Frame time is measured in jiffies, where 1 jiffy is is about 1/60th of a second. Jiffy durations is strictly related to the CPU clock of given machine.