Compressed video mostly does not store pictures. It stores occasional full frames (keyframes, I-frames) and then, between them, instructions for how pixels move. Datamoshing deletes the keyframes: the decoder keeps applying motion to whatever image it last had, so a new shot’s movement drags the old shot’s pixels around, faces smear into landscapes, and the image melts rather than cuts. A second trick repeats the motion-only frames so a gesture plows the same pixels forward again and again, blooming the frame into abstract sludge.
The look broke into music video culture in the late 2000s (Chairlift’s “Evident Utensil” and Kanye West’s “Welcome to Heartbreak” arriving within weeks of each other) and has cycled between underground technique and mainstream transition effect ever since.
Classic moshing is an offline act of vandalism against a file, hard to control and harder to repeat. Modern tools simulate it live: optical-flow shaders compute motion and misapply it on purpose, giving the smear as a performable, reactive effect with none of the codec roulette. Either way the material is the compression itself, which places datamoshing at the technical heart of glitch art: the medium’s bookkeeping, exposed and played as an instrument.