To understand Xvid, one must first understand its adversarial twin, DivX. In the late 1990s, a hacked version of Microsoft’s MPEG-4 video codec emerged, allowing users to compress full-length films onto a single CD-ROM. This became known as DivX ;-) (later DivX). However, when the creators of DivX turned their project into closed-source commercial software, a group of developers forked the last open version to create (Divx spelled backward).