Adaptive Loop Filtering (ALF) is a post-processing technique used in video coding to improve the visual quality of compressed video by reducing visual artifacts. It uses a filter that adapts its parameters based on the characteristics of the video signal, allowing it to effectively reduce artifacts while preserving details and sharpness in the image. ALF is commonly used in modern video codecs such as HEVC, AV1, and VP9, and can help reduce the bitrate required for a given level of visual quality, thus reducing storage and bandwidth requirements for video transmission.